Liu Chuanbin, Hu Bo, Chen Shulin, Glass Richard W
Energy & Environmental Research Center, University of North Dakota, Gand Forks, ND 58203, USA.
Appl Biochem Biotechnol. 2007 Apr;137-140(1-12):875-84. doi: 10.1007/s12010-007-9104-9.
The major challenge associated with the rapid growth of the ethanol industry is the usage of the coproducts, i.e., condensed distillers solubles (CDS) and distillers dried grains, which are currently sold as animal feed supplements. As the growth of the livestock industries remains flat, alternative usage of these coproducts is urgently needed. CDS is obtained after the removal of ethanol by distillation from the yeast fermentation of a grain or a grain mixture by condensing the thin stillage fraction to semisolid. In this work, CDS was first characterized and yeast biomass was proven to be the major component of CDS. CDS contained 7.50% crude protein but with only 42% of that protein being water soluble. Then, CDS was applied as a nutrient supplement for simultaneous production of nisin and lactic acid by Lactococcus lactis subsp. lactis (ATCC 11454). Although CDS was able to support bacteria growth and nisin production, a strong inhibition was observed when CDS was overdosed. This may be caused by the existence of the major ethanol fermentation byproducts, especially lactate and acetate, in CDS. In the final step, the CDS based medium composition for nisin and lactic acid production was optimized using response surface methodology.
与乙醇行业快速发展相关的主要挑战是副产品的利用，即浓缩酒糟可溶物（CDS）和酒糟干粒，它们目前作为动物饲料补充剂出售。由于畜牧业的增长保持平稳，迫切需要这些副产品的替代用途。CDS是通过蒸馏从谷物或谷物混合物的酵母发酵液中去除乙醇后，将稀酒糟馏分浓缩成半固体而获得的。在这项工作中，首先对CDS进行了表征，并证明酵母生物质是CDS的主要成分。CDS含有7.50%的粗蛋白，但其中只有42%的蛋白是水溶性的。然后，将CDS用作乳酸乳球菌乳酸亚种（ATCC 11454）同时生产乳酸链球菌素和乳酸的营养补充剂。虽然CDS能够支持细菌生长和乳酸链球菌素的生产，但当CDS过量时会观察到强烈的抑制作用。这可能是由于CDS中存在主要的乙醇发酵副产物，尤其是乳酸和乙酸。在最后一步，使用响应面法优化了用于生产乳酸链球菌素和乳酸的基于CDS的培养基组成。
