Optimization of the industrial production of bacterial aamylase in Egypt. V. Analysis of kinetic data for enzyme production by two strains of Bacillus amyloliquefaciens

A kinetic study was conducted for a-amylase production process in shake flasks by the wild type strain of Bacillus amyloliquefaciens (strain 267) and in the fermentor by the amplified variant of the sameorganism (strain 267CH). a-Amylase was produced concurrently with growth up to about 72 h, after which it continued without increase in biomass and, in the case of strain 267 even after biomassdeclined. Application of logistic, Luedeking-Piret and the modified Luedeking-Piret mathematical models to the kinetic data revealed that a-amylase production in both cases occurred through bothgrowth- and non-growth associated mechanisms and that the amount of enzyme produced through non-growth associated mechanism exceeded that produced through growth associated mechanism by 3.5 and 2.3 fold by strains 267 and 267CH, respectively. Although with both strains substrate consumption continued even after growth leveled, the application of the model revealed that the major portion of substrate consumption occurred during growth but that a considerable amount was also consumed after maximum growth was reached, mainly for enzyme production. In the bioreactor, increasing aeration from 1 to 2 vvm increased the overall specific growth rate, the production rate, thespecific production rate, and the specific substrate consumption rate and also shortened the time necessary for maximum production of both biomass and enzyme. The increase in biomass either by prolonging the incubation time or by increasing aeration was accompanied by an increase in enzyme production. However, even after maximum biomass was reached, enzyme production still continued to increase, under both conditions

Optimization of the industrial production of bacterial alpha amylase in Egypt. IV. Fermentor production and characterization of the enzyme of two strains of Bacillus subtilis and Bacillus amyloliquefaciens

Production of alpha amylase using amplified variants of Bacillus subtilis (strain SCH) and of Bacillus amyloliquefaciens (strain 267CH) was conducted in a bioreactor with multiprotein-mineral media. Thetime course of fermentation in a bioreactor revealed that the highest yield (about 8 x 104 U/ml within 60 h) by strain SCH was obtained by applying: 3.5% initial starch, 2% additional starch after 19 h, 3 vvmaeration and 300 rpm agitation. The highest yield (about 19 x 104 U/ml within 100 h) by strain 267CH was obtained by applying: 2.5% initial starch, 2% additional starch after 24 h, 3 vvm aeration, and 300 rpmagitation with the productivity after 60 h reaching only about 14 x 104 U/ml. Production occurred in both the logarithmic and postlogarithmic phases of growth. Maximum consumption of starch and proteinoccurred during the first day of incubation. The optical density peak coincided with enzyme production peak in case of strain SCH and preceded that of enzyme production in case of strain 267CH. The alphaamylase produced by the two strains was shown to be of the liquefying and not the saccharifying type. Both enzymes liquefied starch to a dextrose equivalent of about 15 - 17 at 95oC hence they areclassified among thermostable alpha amylases. They exhibited broad pH and temperature activity profiles. The optimum pH for activity was 4 - 7 for alpha amylase produced by strain SCH and 4 - 8 foralpha amylase produced by strain 267CH while the optimum temperatures for their activities were in the range 37 -75oC at 0.5% starch and in the range 85 - 95oC at 35% starch