Rhizopus oryzae LS1利用丢糟水解液发酵生产乳酸

研究了一株诱变米根霉Rhizopus oryzae LS-1利用丢糟水解液发酵生产乳酸的可行性。首先考察R.oryzae LS-1利用葡萄糖和木糖的糖代谢差异特性,并通过正交实验优化丢糟水解液发酵生产乳酸的工艺参数。结果表明,R.oryzae LS-1能代谢利用葡萄糖和木糖,且二者存在协同互补作用,有利于乳酸生成和糖酸转化,可用于木质纤维原料的乳酸生产。丢糟水解液发酵生产乳酸的实验表明,氯化铵是R.oryzae LS-1适宜的氮源。在接种量为3.0%、p H为6.5、发酵时间为96h、Ca CO3添加量为80g/L的条件下,乳酸生成浓度为13.27g/L,糖利用率为79.61%。说明诱变菌株R.oryzae LS-1具备发酵丢糟水解液制备乳酸的潜力。 

Production of lactic acid from distillers grains hydrolysates by Rhizopus oryzae LS-1

Distillers grains,one of the lignocellulosic biomasses riched in cellulose and hemicellulose,was used as an economically attractive carbohydrate feedstock for production of lactic acid by saccharification and microbial fermentation processes. The aim of this study was to investigate the possibility of lactic acid production from distillers grains hydrolysates by the mutant strain Rhizopus oryzae LS-1 and to optimize the biological conversion of reducing sugars into lactic acid to evaluate the culture conditions. The effects of factors such as inoculations size,Ca CO3 addition,p H value and fermentation time on the lactic acid concentration and the reducing sugars utilization rate were researched by the method of orthogonal experimental design.In addition,the sugar metabolism of R.oryzae LS- 1 was also studied. The results show that R. oryzae LS- 1 has the capability to utilize xylose or glucose as carbon resource,furthermore there are synergic and complementary actions during the coexistence of both sugars. The cooperated operations of metabolism was beneficial to the bioconversion of lignocellulosic biomass for lactic acid production. Fermentation results show that ammonium chloride is the most favorable nitrogen source for lactic acid production,the optimal fermentation conditions are inoculation size of 3.0% seed culture,Ca CO3 addition of 80g·L- 1,fermentation time of 96 h and culture p H of 6.5. Under optimal conditions,13.27 g / L lactic acid was produced and the sugar conversion rate reached 79.61%. This study provided an encouraging means of producing lactic acid from lignocellulosic resource such as the low- cost distillers grains. It was concluded that the fermentation technics for the production of lactic acid from distiller grains was worthy to be developed on a large scale.