Department of Botany and Microbiology, The University of Oklahoma, 770 Van Vleet Oval, Norman, OK, 73019, USA.
World J Microbiol Biotechnol. 2012 Apr;28(4):1553-61. doi: 10.1007/s11274-011-0959-0. Epub 2011 Nov 26.
Fermentation of biomass derived synthesis gas to ethanol is a sustainable approach that can provide more usable energy and environmental benefits than food-based biofuels. The effects of various medium components on ethanol production by Clostridium ragsdalei utilizing syngas components (CO:CO(2)) were investigated, and corn steep liquor (CSL) was used as an inexpensive nutrient source for ethanol production by C. ragsdalei. Elimination of Mg(2+), NH(4) (+) and PO(4) (3-) decreased ethanol production from 38 to 3.7, 23 and 5.93 mM, respectively. Eliminating Na(+), Ca(2+), and K(+) or increasing Ca(2+), Mg(2+), K(+), NH(4) (+) and PO(4) (3-) concentrations had no effect on ethanol production. However, increased Na(+) concentration (171 mM) inhibited growth and ethanol production. Yeast extract (0.5 g l(-1)) and trace metals were necessary for growth of C. ragsdalei. CSL alone did not support growth and ethanol production. Nutrients limiting in CSL were trace metals, NH(4) (+) and reducing agent (Cys: cysteine sulfide). Supplementation of trace metals, NH(4) (+) and CyS to CSL (20 g l(-1), wet weight basis) yielded better growth and similar ethanol production as compared to control medium. Using 10 g l(-1), the nutritional limitation led to reduced ethanol production. Higher concentrations of CSL (50 and 100 g l(-1)) were inhibitory for cell growth and ethanol production. The CSL could replace yeast extract, vitamins and minerals (excluding NH(4) (+)). The optimized CSL medium produced 120 and 50 mM of ethanol and acetate, respectively. The CSL could provide as an inexpensive source of most of the nutrients required for the syngas fermentation, and thus could improve the economics of ethanol production from biomass derived synthesis gas by C. ragsdalei.
利用合成气成分（CO:CO(2)）发酵生物质衍生的合成气生产乙醇是一种可持续的方法，比以粮食为基础的生物燃料提供更多可用能源和环境效益。本研究考察了不同培养基成分对产乙醇梭菌（Clostridium ragsdalei）利用合成气生产乙醇的影响，并使用廉价的玉米浆（CSL）作为产乙醇梭菌的氮源。去除 Mg(2+)、NH(4) (+)和 PO(4) (3-)使乙醇产量分别从 38mM 降低至 3.7、23mM 和 5.93mM。去除 Na(+)、Ca(2+)和 K(+)或增加 Ca(2+)、Mg(2+)、K(+)、NH(4) (+)和 PO(4) (3-)浓度对乙醇产量没有影响。然而，增加 Na(+)浓度（171mM）抑制了生长和乙醇生产。酵母提取物（0.5g/L）和痕量金属是产乙醇梭菌生长所必需的。CSL 本身不能支持生长和乙醇生产。CSL 中的限制营养物质为痕量金属、NH(4) (+)和还原剂（Cys:半胱氨酸硫醚）。在 CSL（20g/L，湿重基础）中补充痕量金属、NH(4) (+)和 CyS 可获得比对照培养基更好的生长和相似的乙醇产量。当使用 10g/L 时，营养限制导致乙醇产量降低。较高浓度的 CSL（50 和 100g/L）对细胞生长和乙醇生产有抑制作用。CSL 可以替代酵母提取物、维生素和矿物质（不包括 NH(4) (+)）。优化的 CSL 培养基分别产生 120mM 和 50mM 的乙醇和乙酸。CSL 可为合成气发酵所需的大部分营养物质提供廉价来源，从而可以提高产乙醇梭菌利用生物质衍生合成气生产乙醇的经济性。
