Kerubo, JO, Muthumbi AWN, Onyari JM, Robertson-Andersson D, Kimani E.  2021.  Microplastics pollution in the sediments of creeks and estuaries of Kenya, western Indian Ocean. African Journal of Marine Science. 43(3):337-352. AbstractAfrican Journal of Marine Science

Microplastic pollution has been recognised as a global threat in marine environments and a danger to prey, predators and humans. Yet, there have been few studies in the western Indian Ocean, specifically along the Kenyan coast, which makes it difficult to estimate the extent of such pollution in the region. This is the first study on microplastics (MPs) in the sediments within creeks and estuaries (Tudor, Port Reitz and Mida creeks) on the Kenyan coast. In January/February and September 2018 sediment samples were collected for MPs analysis. The concentration of MPs differed between the sampling seasons and was distinctively higher in the second sampling season across particle sizes, suggesting that there were more MPs from larger terrestrial discharges due to increased runoff. The concentrations of total MPs, and the occurrence of different sizes, shapes and colours, were established under a microscope …

Isaiah, BM, Onyari JM, Omosa LK.  2021.  Physicochemical Properties, Fatty Acids Composition and Antioxidant Potential of the Seed Kernel Oil of Oysternut (Telfairia pedata) Found in Kenya. European Journal of Medicinal Plants. 32(1):46-56. AbstractEuropean Journal of Medicinal Plants


Aim: Certain edible plant sources contain vegetable oils that have been under-exploited both commercially and in research. This study aimed to determine the physicochemical properties, fatty acids composition, and antioxidant potential of the oil from the seed kernels of Telfairiapedata, which are used as food by the local population of Tharaka-Nithi County in Kenya.

Materials and Methods: Telfairia pedata seeds were collected from farmers in the county of Tharaka-Nithi, Kenya. n-Hexane was used to extract the oil via soxhlet extraction. Standard laboratory protocols were used to characterize the oil’s physicochemical properties, while fatty acids composition and antioxidant potential were characterized using gas chromatography mass spectrometry and 2, 2-diphenyl-1-picrylhydrazyl assay, respectively.

Results: The seed kernels of Telfairia pedata yielded more than 66% of oil. The oil’s physicochemical properties were found to be within the Food and Agriculture Organization set limits and were as follows; moisture content (0.0592±0.0140%), peroxide value (0.9641±0.2021 meq O2/Kg), iodine value (23.0058±2.2473 gI2/100g) and acid value (0.6352±0.0330 mg KOH/g). Fatty acids such as myristic acid (14:0; 0.11%), palmitoleic acid (16:1n7; 0.13%), palmitic acid (16:0; 34.97%), margaric acid (17:0; 0.10%), linoleic acid (18:2n6; 48.46%), stearic acid (18:0; 15.33%), 10,13-octadecadienoic acid (18:2n5; 0.09%), 18-methylnonadecanoic acid (20:0; 0.68%), and behenic acid (22:0; 0.14%) were found in the oil. The antioxidant potential of the oil expressed in IC50 was found to be 18.05 mg/mL, in relation to that of ascorbic acid 2.406 mg/mL.

Conclusions: Telfairia pedata seed kernel oil can be economical to exploit commercially due to its relatively high yield. The determined properties of Telfairiapedata seed kernel oil present high nutritive value making the oil fit for edible applications.

  2021.  Antibacterial Activities and Phytochemical Screening of Crude Extracts from Kenyan Macaranga Species Towards MDR Phenotypes Expressing Efflux Pumps.. Pharmacognosy Communications. 11(2) AbstractPharmacognosy Communications

Macaranga species are traditionally used for the treatment and management of coughing, fungal infection, and wounds. In this study, the phytochemical screening and antibacterial activities of nine crude extracts from Macaranga conglomerata, Macaranga kilimandscharica and Macaranga capensis were determined against 13 bacterial strains expressing multi-drug resistance (MDR) phenotypes.
Phytochemical screening of the extracts were carried out according to the standard methods, while the iodonitrotetrazolium chloride (INT) colorimetric assay was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the plants extracts.
Flavonoids, terpenoids, saponins and coumarins were the major secondary metabolites found in all the plant extracts. The results of antibacterial studies revealed that all the plant extracts displayed good activities with MIC values ranging from 4–128 µg/mL against the tested micro-organisms. Most of the extracts exhibited a bactericidal effect against E. coli, E. aerogenes, K. pneumoniae, P. stuartii, P. aeruginosa, and


Kerubo, JO, Muthumbi AW, Onyari JM, Kimani EN, Robertson-Andersson D.  2020.  Microplastic pollution in the surface waters of creeks along the Kenyan coast, Western Indian Ocean (WIO). Western Indian Ocean Journal of Marine Science. 19(2):75-88. AbstractWestern Indian Ocean Journal of Marine Science

Microplastic pollution has been recognized as a global threat in marine environments and a danger to prey, predators and humans. Yet there have been limited studies in the Western Indian Ocean (WIO) and along the Kenyan coast making it difficult to estimate the extent of such pollution. This is the first study on microplastics (MPs) in the surface waters within creeks (Tudor, Port-Reitz and Mida creeks) in Kenya. Sampling was done in January/February and September 2018 to collect microplastics from surface water. Neuston nets of 500 μm (large) and 250 μm (medium) size were towed for ten minutes and 50 litres of seawater sieved through a 20 μm net (small) in three replicates. The samples were digested in 10% Potassium Hydroxide, sieved, and then filtered with cellulose nitrate membrane microfilters. Concentrations of total microplastics, different shapes and colours were established under a microscope. High concentrations of small size (20-250 μm) MPs were encountered and Tudor and Port Reitz had higher concentrations compared to Mida Creek. The study provides data on microplastic concentrations within the creeks and recommends focussing on small size microplastics for monitoring purposes, which due to their high concentrations can be hazardous to organisms.

Muinde, VM, Onyari JM, Wamalwa B, Wabomba JN.  2020.  Adsorption of malachite green dye from aqueous solutions using mesoporous chitosan–zinc oxide composite material. Environmental Chemistry and Ecotoxicology. 2:115-125. AbstractAbstract

Chitosan–zinc oxide composite with an average size of 33 nm was synthesized by facile chemical precipitation technique for application in the removal of water contaminants such as dyes. Malachite green (MG) was the model colorant for the sorption process. Material characterization was achieved using selected spectroscopic techniques. Elemental analysis results revealed that the material had high concentration levels of Zn (965,000 ± 53.2 mg/kg) compared to Fe (756.5 ± 45.3 mg/kg) and P (166 ± 26.6 mg/kg). Batch adsorption experiments of the dye onto chitosan–ZnO (CS–ZnO) composite was investigated with a UV–Visible photometer. The rate of dye removal was greatly influenced by pH, dye strength, amount of adsorbent and contact time. High removal capacity of 98.5% was achieved with reducing dye strength of 2.3 mg/L, dosage of 0.6 g and pH 8 within 180 min equilibration time. Langmuir model …

Oloo, CM, Onyari JM, Wanyonyi WC, Wabomba JN, Muinde VM.  2020.  Adsorptive removal of hazardous crystal violet dye form aqueous solution using Rhizophora mucronata stem-barks: Equilibrium and kinetics studies. Environmental Chemistry and Ecotoxicology. AbstractEnvironmental Chemistry and Ecotoxicology

Adsorption of crystal violet (CV) dye from aqueous solution using dried bark powder of mangrove species Rhizophora mucronata was studied. Characterization of adsorbent was done using FTIR and SEM. Batch experiment was carried out to examine the viability of using mangrove bark for adsorption of CV dye from aqueous solutions under different process conditions. The result revealed that removal of CV increased with contact time, adsorbent dose, initial dye concentration and decreased with increased particle size and ionic strength. pH 7 was the optimum pH for CV dye removal. The adsorption equilibrium for CV dye by Rhizophora mucronata stem-bark was attained within 60 min with removal efficacy of up to 99.8%. Pseudo-second-order kinetic model was best used to describe sorption kinetics while Freundlich isotherm model was appropriate for describing adsorption isotherm. The results demonstrated …


Chanzu, HA, Onyari JM, Shiundu PM.  2019.  Brewers’ spent grain in adsorption of aqueous Congo Red and malachite Green dyes: Batch and continuous flow systems. Journal of hazardous materials. 380:120897. Abstract


Sorption of Congo Red (CR) and Malachite Green (MG) dyes currently used in pigments and clothing industries were investigated using brewers’ spent grain (BSG) from a local brewery. Adsorption increased with a higher adsorbent weight and lower colorant concentrations. Accumulation of CR and MG was optimal at acidic pH and neutral pH respectively. Sorption decreased with an increase in temperature signifying an exothermic process. Batch adsorption data fitted better to Langmuir adsorption isotherm model and pseudo-second-order kinetics. Maximum monolayer coverage capacities (
were found to be 2.55 mg/g for MG and 36.5 mg/g for CR dye. Column studies using BSG were also conducted for both dyes. Fixed bed breakthrough was fast with an increase in dye concentration, adsorbent surface area, and flow rate and with a decrease in column depth. BSG are effective, simple in design and inexpensive adsorbing material from renewable sources.

Wanyonyi, WC, Onyari JM, Shiundu PM, Mulaa FJ.  2019.  Effective biotransformation of Reactive Black 5 Dye Using Crude Protease from Bacillus Cereus Strain KM201428. Energy Procedia. 157:815-824. Abstract

Effective effluent treatment is a paramount step towards conserving the dwindling clean water resources. The present study describes the use of crude protease extract from Bacillus Cereus Strain KM201428 biotransformation of azo dye Reactive Black 5 (RB5). Batch experimental results displayed over 97% decolorization efficiency with initial dye concentration of 1.0 x 10-4M. The decolorization process was highly dependent on contact time, dye concentration and pH. The optimum contact time and pH for decolorization were 120 hours and pH 9 respectively at 25˚C. Biotransformation of RB5 dye was monitored using UV-Vis spectrophotometer and formed metabolites characterized by LC–QTOF-MS. Comparison of resultant LC–QTOF-MS chromatograms after decolorization confirmed complete cleavage of RB5 dye. First order kinetic fitted well with experimental data for different RB5 dye concentrations


Muinde, VM, Onyari JM, Wamalwa B, Wabomba J, Nthumbi RM.  2017.  Adsorption of malachite green from aqueous solutions onto rice husks: Kinetic and equilibrium studies. Journal of Environmental Protection. 8(03):215. Abstract

A study was done to evaluate the removal of a cationic dye from simulated waste water onto rice husks (RH). Spectroscopic methods such as FTIR and SEM/EDX were used for adsorbent characterization. Experimental dependency on solution pH, initial dye concentration, agitation speed, adsorbentparticle size, temperature of the solution and contact time was evaluated. The adsorption data was tested using both Langmuir and Freundlich isotherms. The data fitted well into Langmuir isotherm model with a monolayer adsorption capacity of 6.5 mg/g. Further, the separation factor (RL) value was less than unity indicating a favorable adsorption process. Adsorption kinetics was determined using pseudo-first-order, pseudo-second-order and intra-particle diffusion models. The results showed that the adsorption of malachite green onto rice husks followed pseudo-second-order model with a determination coefficient of 0.986. This work has revealed that rice husks have a great potential to sequester cationic dyes from aqueous solutions and therefore it can be utilized to clean contaminated effluents.

KIPLAGAT, CHEBONSAMMY, Onyari JM, Mulaa F, wabomba J.  2017.  Extraction and characterization of gelatin from Lates niloticus and potential industrial applications. Biofarmasi Journal of Natural Product Biochemistry. 15(2):53-64. Abstract

Kiplagat CS, Onyari JM, Mulaa F, Wabomba J. 2018. Extraction and characterization of gelatin from Lates niloticus and potential industrial applications. Biofarmasi J Nat Prod Biochem 16: 53-64. This research aims to extract and characterize gelatin from Lates niloticus (Nile perch) scales, then blend it with polyvinyl alcohol (PVA). Hydrolysis of the scales was done using a crude alkaline protease harvested from a bacterium, Bacillus cereus strain wwcp 1, obtained from Lake Bogoria. The lyophilized solution yielded 16.3% of gelatin powder calculated from the dry weight of the scales. The sample was characterized using infrared spectroscopy and showed peaks at 3442 cm-1, 1653 cm-1 and~ 1590 cm-1 corresponding to Amide A, Amide I and Amide II bands respectively. The amino acid analysis shows that glycine was the most abundant amino acid (21.7%), followed by proline (14.6%) and alanine (11.8%). Isoleucine, Histidine, and Tyrosine were the least abundant (1.8, 1.4 and 0.9% respectively). Polyvinyl alcohol-gelatin blend films of various compositions ranging from 10% to 90% PVA were prepared by solution casting method. Differential Scanning Calorimetry (DSC) and Thermo-gravimetric Analysis (TGA) tests showed the films had glass transition, melting and thermal decomposition onset temperatures intermediate between those of the respective individual polymers (PVA and gelatin). The thermal stability of the films reduced with the increase in the amount of the less thermally stable constituent. Lastly, potential applications of the prepared blend films were investigated. Batch experiments to assess the potential of the polymer blend …

Mureithi, AW, Onyari JM, Wanyonyi WC, Mulaa FJ.  2017.  Amino acid Composition of Gelatin Extracted from the Scales of Different Marine Fish Species in Kenya. AbstractFull text link

Gelatin in this study was extracted by an enzymatic process from the scales of three marine fish species; Lutjanus
sebea (Red snapper), Lethrinus harak (Black spot emperor) and Scalus ghobban (Blue barred parrot fish).
Concentration of bacteria for mass production of enzyme was done in a fermentation medium using a bio reactor.
Scales were hydrolyzed at 500C and the pH maintained at 12. Complete hydrolysis took between 20 and 23 days for
all species. The yield for the dried gelatin was between 28.2% and 41.4% for the marine fish scales under study.
Fourier transform infrared spectra showed the presence of amide bands and two other additional absorption bands,
indicating the presence of amide bonds for all the three species. The amino acid composition analysis for the gelatin
of three species was then done showing the presence of 16 amino acids. Glycine was the most abundant for all the
three species with about 35% followed by Alanine both adding up to around 50% of the total amino acid
compositions. The amount of Proline was high for red snapper at over 14.2% compared to 11.1% and 11.6% for
blue barred parrot fish and black spot emperor respectively.

Wabomba, JN, Shiundu PM, Onyari JM, Yanful E.  2017.  Equilibrium and Kinetic Studies of Cu(Ii) Removal from Aqueous Solutions Using a Kenyan Micaceous Mineral.. AbstractFull text link

Copper (II) sorption on a Kenyan micaceous mineral (Mica-K) was studied in the batch mode. The effects of different experimental parameters such as; initial concentration, contact time, sorbent dose, pH, particle size, agitation speed, competition and temperature on the kinetics of copper removal were studied. The sorption pattern of copper onto Mica-K followed Langmuir and Freundlich isotherms. Thermodynamic parameters for copper sorption on Mica-K were also determined. X-ray photoelectron spectroscopic (XPS) analysis of metal ion-equilibrated Mica-K, demonstrated that copper, cadmium and Zinc containing nodules existed on the surface of Mica-K.

Wanyonyi, WC, Onyari JM, Shiundu PM, Mulaa FJ.  2017.  Biodegradation and Detoxification of Malachite Green Dye Using Novel Enzymes from Bacillus cereus Strain KM201428: Kinetic and Metabolite Analysis. AbstractFull text link

Enzyme based degradation of organic pollutants is a promising detoxifying approach due to the promiscuous nature of the enzyme, efficiency, cost effective and ecofriendly. In the present study, we have carried out detailed decoloration and degradation studies on a model triphenyl methane group of dyes (Malachite Green dye (MG)) using a newly isolated enzyme from Bacillus cereus KM201428 under the static condition. Biodegradation of dyes was monitored by UV-VIS spectrophotometer and the resultant metabolites analyzed by Liquid Chromatography–Hybrid Quadrupole Time of Flight Mass Spectrometry (LC–QToF-MS) and Gas Chromatography/Mass Spectrometry (GC - MS). Metabolite analysis results revealed that enzymatic degradation of MG dye resulted in complete mineralization and benzene ring-removal; the latter known for organic dye toxicity. Kinetic study results revealed that first-order kinetic model was best applicable for describing MG dye decoloration. Michaelise-Menten kinetics, Lineweaver–Burk plot and Eadie-Hofstee plot models were used to establish the kinetic parameters for the dye decoloration. Lineweaver–Burk plot provided the best theoretical correlation of the experimental data with maximum rate (Vmax) of 17.70 mg l-1h-1 and Michaelis constant (Km) of 124 mgl-1. Results provide evidence that crude enzyme from Bacillus cereus strain KM201428 offers an effective, renewable, ecofriendly and affordable biotechnology for treatment of industrial effluents polluted with organic dye.


This paper highlights how human settlements aligned themselves to share the benefits to arise from coastal tourism development in
the Kenya coast, but have come to bedevil the industry through poor management of domestic waste. The study area comprised of
Nyali-Bamburi-Shanzu and Diani-Chale, which are two important tourist destinations in the country. It attempted to establish
population numbers in these habitations, the waste loads generated, and how it was managed. The study was accomplished through
field visits, library research and application of the World Health Organization (WHO 1989) rapid assessment methods for land, air
and water pollution. The relevant data for assessment was obtained from records of population census, bed nights, occupancy, and the
waste disposal methods in use. The study revealed that human settlements aligned themselves in clusters inland, reflecting the clusters
of the beach hotels dotting the shore line of the Indian Ocean. Large volumes of domestic waste were being generated in both the
human settlements and in the hotels. Management of the waste in the settlements was largely on-site and mixed, through the use of
both pit latrines and septic-tank/soakage pit systems in the human settlements, and only through septic-tank/soakage pits in the hotel
establishments. None of the settlements had wastewater treatment facilities. Only 5 beach hotels had wastewater treatment plants.
While the settlements positioned themselves to benefit from the tourism industry, tapping in business and employment opportunities,
the arrangement has seemed to spoil the broth as the settlements came to be the main source domestic waste affecting environmental
quality and undermining tourism growth and sustainability. Also, through the large number of visitors, during the peak tourist periods,
the beach hotels themselves have come contribute to large waste generation. On-site sanitation, it is concluded, is not appropriate for
managing domestic waste in coastal areas dependent on good quality environmental to flourish the tourism economic sector. Tourism
thrives in areas where the environment is aesthetically appealing; domestic waste undermine. Consequently, it is recommended that
innovative approaches are pursued for domestic waste management in order to flourish and sustain the industry.

Muinde, VM, Onyari JM, Wamalwa B, Wabomba J, Nthumbi RM.  2017.  Adsorption of Malachite Green from Aqueous Solutions onto Rice Husks: Kinetic and Equilibrium Studies. Journal of Environmental Protection. 8(03):215. AbstractWebsite

A study was done to evaluate the removal of a cationic dye from simulated waste water onto rice husks (RH). Spectroscopic methods such as FTIR and SEM/EDX were used for adsorbent characterization. Experimental dependency on solution pH, initial dye concentration, agitation speed, adsorbentparticle size, temperature of the solution and contact time was evaluated. The adsorption data was tested using both Langmuir and Freundlich isotherms. The data fitted well into Langmuir isotherm model with a monolayer adsorption capacity of 6.5 mg/g. Further, the separation factor (RL) value was less than unity indicating a favorable adsorption process. Adsorption kinetics was determined using pseudo-first-order, pseudo-second-order and intra-particle diffusion models. The results showed that the adsorption of malachite green onto rice husks followed pseudo-second-order model with a determination coefficient of 0.986. This work has revealed that rice husks have a great potential to sequester cationic dyes from aqueous solutions and therefore it can be utilized to clean contaminated effluents.


W.O.Osawa, Sahoo PK, J.M.Onyari, F.J.Mulaa.  2015.  Effects of antioxidants on oxidation and storage stability of Croton megalocarpus biodiesel.. International Journal of Energy and Environmental Engineering. Abstractart3a10.10072fs40095-015-0191-z.pdf

The effects of antioxidants and storage on
oxidation stability of croton biodiesel and its blends with
petro-diesel were determined using PetroOxy equipment.
The biodiesel and blends were kept in Pyrex reagent bottles
and stored in a metallic locker at room temperature for
8 weeks, a condition that imitated ordinary storage environment
in tanks before use. The oxidation stability indices
of the biodiesel and blends were determined by measuring
Rancimat induction periods for 8 weeks at intervals of
2 weeks. Although the Rancimat induction period for
freshly prepared biodiesel of 4 h was higher than the
commonly used American standard (ASTM D6751) limit
of 3 h, it was lower than the European standard (EN 14214)
of 6 h. The induction periods of B50 and lower blends
were, however, equal to or greater than 6 h. The Rancimat
induction periods for biodiesel with 100 ppm antioxidants
were 5.6, 6.8 and 7.8 h for Butylated hydroxyanisol
(BHA), Propyl gallate (PRG) and Pyrogallol (PYG),
respectively, while the Rancimat induction periods for
biodiesel with 1000 ppm antioxidants were 6.8, 8.2 and
10 h for BHA, PRG and PYG, respectively. The oxidation
stability index for neat biodiesel decreased by 45 % while
that for biodiesel with 1000 ppm antioxidants depreciated
by 16, 12.2 and 20.59 % for PYG, PRG and BHA,
respectively, during the 8-week storage period. A more
rapid decline in oxidation stability was observed in the
biodiesel and blends without antioxidants than those with
antioxidants. The results from this study showed that the
use of appropriate concentrations of suitable antioxidants
can greatly improve the oxidation stability of biodiesel and
blends which can therefore be stored over longer periods of
time before use without undergoing extensive and deleterious
oxidative deterioration.
Keywords Croton biodiesel Oxidation stability
Antioxidants Storage stability

Osawa, WO, Sahoo FK, Onyari J, Mulaa F.  2015.  Experimental Investigation on performance,emission and combustion characteristics of Croton Megalocarpus of Biodiesel Blends in a Direct injection Diesel Engine. International Journal of Science and International Technology. 4(1):26-33. Abstract6488141691776.pdf

The emission, performance and combustion characteristics of croton biodiesel blends were tested in a direct injection (DI) single
cylinder four stroke diesel engine. The physico-chemical properties of the biodiesel blends were all found to be within the standard
ASTM values. The reduction in exhaust smoke emissions for the biodiesel blends ranged from 10% to 41% at maximum engine load
of 10 Kg while a slight increase in NOx emissions was observed with increase in concentration of biodiesel in the blends. Similar
general increase in brake thermal efficiency (BTE), temperature of exhaust emissions and fuel flow rate was observed with increasing
engine load for both petro-diesel and biodiesel blends. The difference between BTE for petro-diesel and biodiesel blends ranged from
2.04 to 5.03%. The brake specific energy consumption (BSEC) decreased with increasing engine load for both petro-diesel and
biodiesel blends. An increase in both engine pressure and heat released was observed with increase in concentration of biodiesel in the
blends. The difference in maximum engine pressure ranged from 1.05 bar at 0 Kg to 3.77 bar at 10 Kg load. The greatest difference in
maximum engine pressure was recorded between petro-diesel and B50 blend. The observed difference in position of peaks for
maximum heat released showed that there was slight delay in ignition of biodiesel blends as compared to petro-diesel. The results
obtained in this study showed that higher blends of up to 50% biodiesel can be effectively used as an alternative to petro-diesel without
compromising the engine performance.
Key words:Croton biodiesel blends, Diesel engine, Emission and performance characteristics.


Anzeze DA, Onyari JM, SPMGPW.  2014.  Adsorption of Pb (II) ions from aqueous solutions by water hyacinth (Eichhornia crassipes): Equilibrium and Kinetic studies,. International Journal of Environmental Pollution and Remediation. Volume 2,(DOI: 10.11159/ijepr.2014):9p.
Anzeze DA, Onyari JM, SPMGJW.  2014.  Biosorption of Zn (II) ions from aqueous solutions by water hyacinth (Eichhornia crasippes): Equilibrium and Kinetic studies,. International Journal of Innovation and Scientific Research,. Vol. 8(No. 2 Sep. 2014,):224-233.
Wanyonyi WC, Onyari JM, SPM.  2014.  Adsorption of Congo Red Dye from Aqueous Solutions Using Roots of Eichhornia crassipes: Kinetic and Equilibrium Studies. The International Conference on Technologies and Materials for Renewable Energy, Environment and Sustainability, TMREES14, Energy Procedia. 50:862–869.
Anzeze DA, Onyari JM, SPMGJW.  2014.  Equilibrium and Kinetics studies for the biosorption of aqueous Cd (II) ions onto Eichhornia crasippes biomass,. IOSR Journal of Applied Chemistry. Volume 7(Issue 1 Ver. II. (Feb. 2014)):29-37.
Shee Ali, Onyari JM, WJNMD.  2014.  Methylene Blue Adsorption onto Coconut husks/Polylactide Blended Films: Equilibrium and Kinetic Studies. Chemistry and Materials Research. Vol.6(No.11):28-37.
Osawa W.O, Onyari JM, SPKMFJ.  2014.  Process optimization for production of biodiesel from croton oil using two-stage process. IOSR Journal of Environmental Science, Toxicology and Food Technology. Volume 8(Issue 11 Ver. III (Nov. 2014)):49-54.
Wanyonyi WC, Onyari JM, SPMMFJ.  2014.  Enzymatic Decolorization of Malachite Green Dye by a Newly Isolated Bacillus Cereus Strain wwcp1. IOSR Journal of Environmental Science, Toxicology and Food Technology. Vol 8(Issue 12 Ver. III (Dec. 2014)):58-64..


Onyari, JM, Addis Teshome, Suresh K. Raina, Kabaru JM, Fritz Vollrath, Suresh K. Raina.  2013.  Mechanical and thermal degradation properties of silk from African wild silkmoths. AbstractFull text link

Variations among silk of four African wild silkmoths, Argema mimosae, Anaphe panda, Gonometa postica, and Epiphora bauhiniae, was studied regarding their mechanical properties and thermal degradation behaviors. Cocoon shells and individual degummed fibers were examined using tensile testing, thermogravimetric analysis, and scanning electron microscope (SEM). A. mimosae and G. postica cocoon shells had marginally higher initial moduli and strains at maximum stress. The stress–strain curves of Bobmyx mori and A. panda degummed fibers lacked clear yielding points. G. postica fibers had the highest breaking energy (76.4 J/cm3) and breaking strain (41.3%). The ultimate tensile strength was the highest for B. mori (427 MPa). Fiber pull-out and detachment was predominant in fracture surfaces of both the cocoon shells and the fibers. Wild cocoon shells and degummed fibers had higher temperature for dehydration loss than B. mori. A. mimosae fibers (11.9%) and G. postica cocoon shells (13.3 %) had the highest weight loss due to dehydration. E. bauhinae cocoon shells and B. mori fibers had the highest total weight losses of 97.2 and 93.4%, respectively. The African silks exhibited variations in their mechanical and thermal degradation properties related to their physical and chemical structure and composition. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013


David M. Maina, Lydia W. Njenga, John M. Onyari, Kyalo BN.  2012.  Trace Element Concentrations in Some Traditional Diets Consumed in Selected Parts of Eastern Province of Kenya. Journal of Environmental Protection. 3
Teshome, 3. A, Fritz Vollrath, Suresh K. Raina, J.M. Kabaru, Onyari J.  2012.  Study on the microstructure of African wild silk cocoon shells and fibers. Journal of Biological Macromolecules. 50 :63–68.
Addis Teshome, Onyari JM, Raina SK, Jacques M. Kabaru, Fritz Vollrath, Suresh K. Raina.  2012.  Mechanical and Thermal Degradation Properties of Silk from African Wild Silkmoths. J. APPL. POLYM. SCI. (DOI: 10.1002/APP.37873):5-15.
Harry Amuguni Chanzu • John Mmari Onyari, Shiundu PM.  2012.  ), Biosorption of Malachite Green from Aqueous Solutions onto Polylactide/Spent Brewery Grains Films: Kinetic and Equilibrium Studies. J Polym Environ. DOI 10.1007/s10924-012-0479-5


Nyatebe, JO, Njenga GK, Wandiga SO, Orata F, Oduor FDO, Onyari JM.  2011.  A survey of heavy metal pollution from automotive emmissions in Kenya's urban Environment. Full text link
Teshome A, Raina SK, Vollrath F, Kabaru JM, Onyari J, EK N, Nguku.  2011.  Study on weight loss and moisture regain of Silk Cocoon shells and Degummed Fibers from African Wild Silkmoths. Journal of Entomology . 8(5):450-458.
Maube OM, Nyang’aya JA, JM, Onyari.  2011.  Evaluation of Chemical and Physical Properties of Biodiesel Produced from Used Edible Vegetable Oil. Journal of Agriculture, Pure and Applied Science and Technology. (ISSN 2073-8749):14p.
Kimilu R.K, Nyang’aya J.A, Onyari JM.  2011.  The effect of Temperature and blending on the specific gravity and viscosity of Jatropha Methyl ester. Journal of Engineering and Applied Sciences. 6(12):97-105.


Nguta, CM, WO O, Onyari, Onyiego.  2010.  ). Levels of Selected Heavy Metals & Fluoride in water around Fluorspar Factory in Kerio Valley, Kenya. Kenya J Sci Tech Inn. . 1:12-22.
Dharani N, Onyari JM, Kinyamario JI, Maina, Mavuti.  2010.  Distribution of Cd and Zn levels in Soils and Acacia xanthophloea Benth. From Lake Nakuru National Park, Kenya. Bulletin of Environmental Contamination and Toxicology. 85(3):318-323.


Nyunja, J, Ntiba M, Onyari J, Mavuti K, Soetaert K, Bouillon S.  2009.  Autotrophic carbon sources for fish communities in a tropical coastal ecosystem (Gazi bay, Kenya). Website
Nyunja, J, M. Ntiba, J. Onyari, K. Mavuti, Bouillon S.  2009.  Carbon sources supporting a diverse fish community in a tropical coastal ecosystem (Gazi Bay, Kenya). Estuarine, Coastal and Shelf Science. 83(3):265-378.
Onyari, JM, Huang SJ.  2009.  Synthesis and Properties of Novel Polyvinyl alcohol-Lactic acid Gels. Journal of Applied Polymer Science . 113:2053-2061.


JM, O, Mulaa F, J M, P S.  2008.  Biodegradability of PLA, Preparation and Properties of PLA/Gum Blends. Journal of Polymers and the Environment. 16:205-212.

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