Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam, India.
Department of Civil Engineering, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam, India.
Bioresour Technol. 2017 Nov;244(Pt 1):362-370. doi: 10.1016/j.biortech.2017.07.136. Epub 2017 Jul 27.
In present study, statistical optimization of biodiesel-derived crude glycerol fermentation to DHA by immobilized G. oxydans cells over polyurethane foam is reported. Effect of DHA (product) inhibition on crude glycerol fermentation was analyzed using conventional biokinetic models and new model that accounts for both substrate and product inhibition. Optimum values of fermentation parameters were: pH=4.7, temperature=31°C, initial substrate concentration=20g/L. At optimum conditions, DHA yield was 89% (17.83g/L). Effect of product inhibition on fermentation was trivial for DHA concentrations ≤30g/L. At higher concentrations (≥50g/L), kinetics and yield of fermentation showed marked reduction with sharp drop in V and K values. Inhibition effect was more pronounced for immobilized cells due to restricted transport of fermentation mixture across polyurethane foam. Retention of fermentation mixture in immobilized matrix resulted in higher localized DHA concentration that possibly enhanced inhibition effect.
本研究报告了通过固定化 G. oxydans 细胞在聚氨酯泡沫上对生物柴油衍生粗甘油发酵生产 DHA 的统计优化。使用传统生物动力学模型和新模型分析了 DHA（产物）抑制对粗甘油发酵的影响，该模型同时考虑了底物和产物抑制。发酵参数的最佳值为：pH=4.7，温度=31°C，初始底物浓度=20g/L。在最佳条件下，DHA 的产率为 89%（17.83g/L）。对于 DHA 浓度≤30g/L，产物抑制对发酵的影响微不足道。在更高的浓度（≥50g/L）下，发酵的动力学和产率明显下降，V 和 K 值急剧下降。由于发酵混合物在聚氨酯泡沫中的传输受到限制，固定化细胞的抑制作用更为明显。发酵混合物在固定化基质中的保留导致局部 DHA 浓度升高，从而可能增强抑制作用。
