pH对米根霉发酵厨余垃圾生产L-乳酸的影响

Effect of pH on Yield of Lactic Acid from Kitchen Wastes Fermentation by Rhizopus Oryzae AS 3.819

为了强化厨余垃圾发酵L-乳酸的产量和光学纯度,研究了pH对米根霉AS3.819发酵厨余垃圾生产乳酸及其光学特性的影响。结果表明,在中温条件下(34℃),米根霉生长的最适pH为7,最适发酵条件为8。用米根霉发酵非灭菌的厨余垃圾生产乳酸,发酵液中还原糖浓度低,且呈先升高,后下降到最低的趋势。pH调节到近中性和偏碱性(pH6、7、8)的各组还原糖浓度高于偏酸性组(pH 5和对照组)。控制pH为8时,总乳酸产生速率达1 g/(L·h),L-乳酸是主要的异构体形式,L-乳酸在总乳酸中的比例在整个发酵时间段内都保持在0.75以上,L-乳酸浓度最高达到59.8 g/L,L-乳酸光学纯度可达到0.99。控制pH为8时,可以同时获得高的乳酸产量和光学纯度。

In order to realize resource recycling of kitchen waste, the enhancement of fermentative production of lactic acid（LA）by Rhizopus oryzae AS 3.819 was investigated. Batch experiments were carried out to analyze the effect of pH on the yield of total lactic acid and the distribution of L- and D-lactic acid among total lactic acid during the non-sterilized fermentation of kitchen wastes by rhizopus oryzae AS 3.819. The results showed that when rhizopus oryzae was cultured in medium temperature（34℃）, the optimal growth condition was pH 7, the optimal fermentation condition was pH8. The concentration of reduced sugar（calculated as glucose）was low, and its concentration was higher at neutral and alkali conditions（pH6-8）than at acidic conditions（non-controlled pH and pH5）. The L-lactic acid was the predominant isomer form at pH 8. The maximum total lactic acid production rate was 1g/（L·h）, the ratio of L-lactic acid kept at above 0.75 during the whole experimental fermentation time and reached the maximum value（0.99）at 60 h and the maximum L-lactic acid was 59.8 g/L. To obtain high L-lactic acid yield and optical purity simultaneously, it was suggested that PH should be controlled at 8.