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Conference Paper
J PROFMULAAFRANCIS. "Hydrogen peroxide degradation by immobilized cells of alkaliphilic Bacillus halodurans.". In: Biocatalysis and Biotransformation, 24. 3,. 215-222. Springerlink; 2006.
J PROFMULAAFRANCIS. "Hashim SO, Kaul RH, Andersson M, Mulaa FJ, Mattiasson B.Differential scanning calorimetric studies of a Bacillus halodurans alpha-amylase.Biochim Biophys Acta. 2005 May 25;1723(1-3):184-91. Epub 2005 Mar 24.". In: Biochim Biophys Acta. 2005 May 25;1723(1-3):184-91. Epub 2005 Mar 24. Springerlink; 2005. Abstract
The thermal unfolding of Amy 34, a recombinant alpha-amylase from Bacillus halodurans, has been investigated using differential scanning calorimetry (DSC). The denaturation of Amy 34 involves irreversible processes with an apparent denaturation temperature (T(m)) of 70.8 degrees C at pH 9.0, with four transitions, as determined using multiple Gaussian curves. The T(m) increased by 5 degrees C in the presence of 100-fold molar excess of CaCl2 while the aggregation of Amy 34 was observed in the presence of 1000-fold molar excess of CaCl2. Increase in the calcium ion concentration from 1- to 5-fold molar excess resulted in an increase in calorimetric enthalpy (DeltaH(cal)), however, at higher concentrations of CaCl2 (up to 100-fold), DeltaH(cal) was found to decrease, accompanied by a decrease in entropy change (DeltaS), while the T(m) steadily increased. The presence of 100-fold excess of metal chelator, EDTA, resulted in a decrease in T(m) by 10.4 degrees C. T(m) was also decreased to 61.1 degrees C and 65.9 degrees C at pH 6.0 and pH 11.0, respectively.
J PROFMULAAFRANCIS. "Hashim SO, Delgado O, Hatti-Kaul R, Mulaa FJ, Mattiasson B.Starch hydrolysing Bacillus halodurans isolates from a Kenyan soda lake.Biotechnol Lett. 2004 May;26(10):823-8.". In: Biotechnol Lett. 2004 May;26(10):823-8. Springerlink; 2004. Abstract
Fourteen obligate alkaliphilic and halotolerant bacterial isolates, exhibiting extracellular amylase activity at 55 degrees C and pH 10, were isolated from hot springs around Lake Bogoria, Kenya. From 16S rDNA sequence analysis, nine isolates shared 100% identity with Bacillus halodurans strain DSM 497T, while the rest shared 99% identity with alkaliphilic Bacillus species A-59. PCR of the intergenic spacer region between 16S and 23S rRNA genes (ISR-PCR) divided the isolates into two groups, while tDNA-PCR divided them into three groups. Bacillus halodurans DSM 497T had a different ISR pattern from the isolates, while it had a tDNA-PCR profile similar to the group that shared 99% identity with alkaliphilic Bacillus species A-59. All isolates hydrolysed soluble starch as well as amylose, amylopectin and pullulan. The amylase activity (1.2-1.8 U ml(-1)) in the culture broths had an optimum temperature of 55-65 degrees C, was stimulated by 1 mm Ca2+, and was either partially (16-30%) or completely inhibited by 1 mM EDTA. Activity staining of the cell-free culture supernatant from the isolates revealed five alkaline active amylase bands.

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