Abstract:

Microbial lipids, similar to vegetable oil in their composition, are potential alternative feedstock for biodiesel production and oleochemical industries as well. However, the high costs of microbial lipids production are the major bottleneck. The synthesis of microbial lipids is considered as a partially growth-associated process with inconstant production rates. For the prediction of lipid yield and substrate distribution, a chemostat process was established for lipid production by the oleaginous yeast Rhodosporidium toruloides AS 2.1389 under nitrogen limitation conditions, and a correlation on carbon distribution between lipid and lipid-free cell components was also developed. The maximal lipid yield Y_L^maxand cell mass yield Y_L^maxwere predicted to be 0.51 mol C·(mol C)^-1 and 0.52 mol C·(mol C)^-1, respectively. Together with the element balance analysis, the critical C/N ratio for switching to lipid production was estimated to be 12.1 mol·mol^-1. The prediction for lipid yields was 95.2%—116.7% of those measured experimentally, indicating that the model was reliable.

Key words: fermentation, bioprocess, model, parameter estimation, C/N, microbial lipids

摘要：

微生物油脂作为胞内代谢产物,其脂肪酸组成和植物油类似,是生物柴油和油脂工业理想替代原料。为了进一步了解底物中碳氮比对油脂合成的影响,通过恒化培养的方法,研究了圆红冬孢酵母在不同稀释率条件下,消耗碳氮比和底物在油脂和非油生物量之间的分配以及和油脂得率之间的关系。通过碳、氢、氧和氮的化学反应计量学分析,并根据不同稀释率稳态时所消耗C/N比,构建了底物碳在油脂和非油生物量之间的分配模型。利用实验数据确定了模型参数:最大油脂碳得率Y_L^max为0.51 mol C·(mol C)^-1,最大菌体碳得率Y_L^max为0.52 mol C·(mol C)^-1,促使油脂合成的临界C/N比为12.1 mol C·(mol C)^-1。利用该分配模型预测不同消耗C/N比的油脂得率,预测值为实验值的 95.2%～116.7%,表明模型可靠性较好。

关键词: 发酵, 生物过程, 模型, 参数估值, 碳氮比, 微生物油脂