Uma Maheswar Rao J L, Satyanarayana T
Department of Microbiology, University of Delhi South Campus, Benito Juarez Road, New Delhi 110 021, India.
Bioresour Technol. 2007 Jan;98(2):345-52. doi: 10.1016/j.biortech.2005.12.022. Epub 2006 Feb 10.
By cultivating Geobacillus thermoleovorans in shake flasks containing cane molasses medium at 70 degrees C, the fermentation variables were optimized by 'one variable at a time' approach followed by response surface methodology (RSM). The statistical model was obtained by central composite design (CCD) using three variables (cane-molasses, urea and inoculum density). An overall 1.6- and 2.1-fold increase in enzyme production was achieved in the optimized medium in shake flasks and fermenter, respectively. The alpha-amylase titre increased significantly in cane-molasses medium (60 U ml(-1)) as compared to that in the synthetic medium (26 U ml(-1)). Thus the cost of enzyme produced in cane molasses medium (0.823 euros per million U) was much lower than that produced in the synthetic starch-yeast extract-tryptone medium (18.52 euros per million U). The shelf life of bread was improved by supplementing dough with alpha-amylase, and thus, the enzyme was found to be useful in preventing the staling of bread. Reducing sugars liberated from 20% and 30% raw pearl millet starch were fermented to ethanol; ethanol production levels attained were 35.40 and 28.0 g l(-1), respectively.
通过在70摄氏度下于装有甘蔗糖蜜培养基的摇瓶中培养嗜热栖热放线菌，采用“一次一个变量”的方法并结合响应面法（RSM）对发酵变量进行了优化。通过使用三个变量（甘蔗糖蜜、尿素和接种密度）的中心复合设计（CCD）获得了统计模型。在优化培养基中，摇瓶和发酵罐中的酶产量分别总体提高了1.6倍和2.1倍。与合成培养基（26 U ml⁻¹）相比，甘蔗糖蜜培养基中的α-淀粉酶效价显著提高（60 U ml⁻¹）。因此，在甘蔗糖蜜培养基中生产酶的成本（每百万单位0.823欧元）远低于在合成淀粉-酵母提取物-胰蛋白胨培养基中生产酶的成本（每百万单位18.52欧元）。通过在面团中添加α-淀粉酶可延长面包的保质期，因此，发现该酶可用于防止面包老化。从20%和30%的生珍珠粟淀粉中释放的还原糖被发酵成乙醇；乙醇产量分别达到35.40和28.0 g l⁻¹。
