Investigation of α-amylase production with bacteria strains at different and medium conditions

ABSTRACT PhD Thesis INVESTIGATION OF ot-AMYLASE PRODUCTION WITH VARIOUS BACTERIA STRAINS AT DIFFERENT PROCESS AND MEDIUM CONDITIONS Muhammet Şaban TANYILDIZI Fırat University Graduate School of Natural and Applied Sciences Department of Chemical Engineering 2005, Page: 119 In this study, the effect of medium conditions on production of a-amylase by Bacillus subtilis IMG22 and Bacillus amyloliquefaciens NRRL B-645 were studied. In the first part of the study, the effects of carbon, nitrogen sources and other medium components on production a-amylase were investigated in synthetic media for both microorganisms. It was found that the production of a-amylase was increased with the use of starch as carbon source for both of microorganisms. Although the production of enzyme with B. subtilis was increased by using glycerol, the production of enzymes decreased with using B. amyloliquefaciens with glycerol. It was observed that inorganic nitrogen sources could not be used by microorganisms. However, enzyme production increased by using organic nitrogen sources by both microorganisms. The results showed that the calcium ions were required in the production of a-amylase called metalloenzyme. From the results of optimization experiments, it was concluded that the maximum enzyme activity value obtained using B. amyloliquefaciens was higher than that obtained with B. subtilis. Maximum enzyme activity (1333 IU) was obtained in the medium containing 15 g/1 starch, 2.5 g/l pepton, 1 g/1 yeast extract, Ig KH2PO4, 0.5 g/1 MgS04.7H20, 0.1g/lCaCl2. In the second part of the work, molasses, sugar beet pulp, sunflower pulp, wheat bran, carob, corn bran, corn protein were used as substrates for solid state fermentation. B. amyloliquefaciens which provides the highest enzyme activity in synthetic medium was used as microorganism in the solid state fermentation. The highest production of a-amylase was obtained in the experiments conducted with corn protein and corn bran. The effects of other medium parameters were investigated by using these substrates. Medium temperature was determined as most influencing parameter on production of a-amylase in solid state fermentation. It was determined that enzyme activities obtained by using natural substrates wereVI higher than those obtained in synthetic medium. Maximum enzyme production was obtained as 8829 IU in fermentation medium containing 10 g/1 yeast extract, 25 g/1 corn bran, 1 g/1 KH2P04 at 33°C and 150 rpm. However, this value was found to be 8388 IU in medium containing 10g/l yeast extract and 30 g/1 corn protein at 33°C, 150 rpm. There was not significant effect of the other medium components on a-amylase production in solid state fermentation. This shows that other medium components which are necessary for a-amylase production in synthetic medium exist in natural substrates and tap water. Keywords: a-Amylase, Microbial enzyme production, B. subtilis, B. amyloliquefaciens, Solid state fermentation..