Abstract：
OBJECTIVE: The objective of this study was to investigate the effects of medium composition on CO fermentation by Clostridium carboxidivorans. The focus was to reduce the medium cost preserving acceptable levels of solvent production.
METHODS: Yeast extract (YE) concentration was set in the range of 0-3 g/L. Different reducing agents were investigated, including cysteine-HCl 0.6 g/L, pure cysteine 0.6 g/L, sodium sulphide (Na2S) 0.6 g/L, cysteine-sodium sulphide 0.6 g/L and cysteine-sodium sulphide 0.72 g/L. The concentration of the metal solution was decreased down to 25 % of the standard value. Fermentation tests were also carried out with and without tungsten or selenium.
RESULTS: The results demonstrated that under optimized conditions, namely yeast extract (YE) concentration set at 1 g/L, pure cysteine as the reducing agent and trace metal concentration reduced to 75 % of the standard value, reasonable solvent production was achieved in less than 150 h. Under these operating conditions, the production levels were found to be 1.39 g/L of ethanol and 0.27 g/L of butanol. Furthermore, the study revealed that selenium was not necessary for C. carboxidivorans fermentation, whereas the presence of tungsten played a crucial role in both cell growth and solvent production.
CONCLUSIONS: The optimization of the medium composition in CO fermentation by Clostridium carboxidivorans is crucial for cost-effective solvent production. Tuning the yeast extract (YE) concentration, using pure cysteine as the reducing agent and reducing trace metal concentration contribute to reasonable solvent production within a relatively short fermentation period. Tungsten is essential for cell growth and solvent production, while selenium is not required.
METHODS: Yeast extract (YE) concentration was set in the range of 0-3 g/L. Different reducing agents were investigated, including cysteine-HCl 0.6 g/L, pure cysteine 0.6 g/L, sodium sulphide (Na2S) 0.6 g/L, cysteine-sodium sulphide 0.6 g/L and cysteine-sodium sulphide 0.72 g/L. The concentration of the metal solution was decreased down to 25 % of the standard value. Fermentation tests were also carried out with and without tungsten or selenium.
RESULTS: The results demonstrated that under optimized conditions, namely yeast extract (YE) concentration set at 1 g/L, pure cysteine as the reducing agent and trace metal concentration reduced to 75 % of the standard value, reasonable solvent production was achieved in less than 150 h. Under these operating conditions, the production levels were found to be 1.39 g/L of ethanol and 0.27 g/L of butanol. Furthermore, the study revealed that selenium was not necessary for C. carboxidivorans fermentation, whereas the presence of tungsten played a crucial role in both cell growth and solvent production.
CONCLUSIONS: The optimization of the medium composition in CO fermentation by Clostridium carboxidivorans is crucial for cost-effective solvent production. Tuning the yeast extract (YE) concentration, using pure cysteine as the reducing agent and reducing trace metal concentration contribute to reasonable solvent production within a relatively short fermentation period. Tungsten is essential for cell growth and solvent production, while selenium is not required.
摘要：
目的：本研究的目的是研究培养基组成对羧化梭菌CO发酵的影响。重点是降低介质成本，保持可接受的溶剂生产水平。.
方法：将酵母提取物（YE）浓度设定在0-3g/L的范围内。研究了不同的还原剂，包括半胱氨酸-HCl0.6g/L，纯半胱氨酸0.6g/L，硫化钠（Na2S）0.6g/L，半胱氨酸-硫化钠0.6g/L和半胱氨酸-硫化钠0.72g/L金属溶液的浓度降低到标准值的25%。还在有和没有钨或硒的情况下进行发酵测试。
结果：结果表明，在优化条件下，即酵母提取物（YE）浓度设定为1g/L，纯半胱氨酸作为还原剂和痕量金属浓度降低到标准值的75%，在不到150小时内实现合理的溶剂生产。在这些操作条件下,发现生产水平为1.39g/L的乙醇和0.27g/L的丁醇。此外，这项研究表明，硒不是羧甲梭菌发酵所必需的，而钨的存在在细胞生长和溶剂产生中起着至关重要的作用。
结论：在羧化梭菌的CO发酵中，培养基组成的优化对于具有成本效益的溶剂生产至关重要。调整酵母提取物（YE）浓度，使用纯半胱氨酸作为还原剂并降低痕量金属浓度有助于在相对较短的发酵时间内合理地生产溶剂。钨对电池生长和溶剂生产至关重要，而硒不是必需的。
方法：将酵母提取物（YE）浓度设定在0-3g/L的范围内。研究了不同的还原剂，包括半胱氨酸-HCl0.6g/L，纯半胱氨酸0.6g/L，硫化钠（Na2S）0.6g/L，半胱氨酸-硫化钠0.6g/L和半胱氨酸-硫化钠0.72g/L金属溶液的浓度降低到标准值的25%。还在有和没有钨或硒的情况下进行发酵测试。
结果：结果表明，在优化条件下，即酵母提取物（YE）浓度设定为1g/L，纯半胱氨酸作为还原剂和痕量金属浓度降低到标准值的75%，在不到150小时内实现合理的溶剂生产。在这些操作条件下,发现生产水平为1.39g/L的乙醇和0.27g/L的丁醇。此外，这项研究表明，硒不是羧甲梭菌发酵所必需的，而钨的存在在细胞生长和溶剂产生中起着至关重要的作用。
结论：在羧化梭菌的CO发酵中，培养基组成的优化对于具有成本效益的溶剂生产至关重要。调整酵母提取物（YE）浓度，使用纯半胱氨酸作为还原剂并降低痕量金属浓度有助于在相对较短的发酵时间内合理地生产溶剂。钨对电池生长和溶剂生产至关重要，而硒不是必需的。
