一株高产乳酸鼠李糖乳杆菌的选育

Breeding of a Lactobacillus rhamnosus Strain with the High Yield Fermentation of L-Lactic Acid

采用紫外线和Co60照射联合诱变鼠李糖乳杆菌(Lactobacillus rhamnosus)JCM1553菌株,选育得到1株L-乳酸高产突变株SCT-10-10-60。经77代传代培养证实该菌株L-乳酸发酵遗传稳定。在37℃,200rpm下,该菌株摇瓶发酵葡萄糖60h的发酵液乳酸浓度达到最大,为195.67g/L,发酵糖酸转化率达到95.33%,比出发菌株最大乳酸产量、发酵速率和糖酸转化率分别提高了16.24%、50.13%和17.81%。相同条件下该菌株发酵木薯淀粉84h的乳酸浓度达到最大值,为203.33g/L,糖酸转化率达到78.85%,比出发菌株最大乳酸产量和发酵速率均提高了29.49%,糖酸转化率则提高24.53%。该菌株发酵产物的L-乳酸含量高达96.75%,与出发菌株(96.97%)无统计学显著差异(P>0.05)。该高产菌株乳酸发酵性能提高的主要原因是菌体增长速率加快。其L-乳酸发酵性能显著优于现有的生产菌株,具有较高的潜在工业价值。

A high yield mutant strain of lactic acid fermentation, defined as SCT-10-10-60, was selected by mutagensis of Lactobacillus rharnnosus JCM1553 strain with the combination of UV and Co60 radiation. The result of 77 generation transfer culture verified the strain had the genetic stability on lactic acid fermentation. In the shave flask fermentation with glucose as substrate under the condition of 37℃ ,200rpm,the lactic acid concentration of mutant strain in broth was reached to maximum of 195.67g/L at 60h of fermentation and the maximum ratio of glucose converting to lactic acid reached to 95. 33%. The maximum lactic acid yield, the fermentation rate and the ratio of glucose converting to lactic acid of mutant strain were respectively 16. 24%,50.13% and 17.81% higher than that of start strain. In the fermentation with enzymatic hydrant of cassava starch as substrate under the same condition, the lactic acid concentration of mutant strain was reached to 203.33g/L of maximum at 84h fermentation, with the maximum lactic acid yield and the [ermentation rate of mutant strain both zg. 49 Y0 higher than that of start strain （157. 02g/L, 84h） ,and the maximum ratio oi glucose converring to lactic acid reached to 78. 85%, 24. 53% higher than that of start strain（63.32%）. The L-lactic acid concentration in the fermentation product of mutant strain, determined by using chiral column HPLC,was high to 96.75% and had not statistical significant difference with the start strain （96.97%） ,indicating that SCT-10-10-60 was a L-lactic acid high-yield strain. How-ever,the calculation of L-lactic acid yield per cell biomass showed that the L-lactic acid yield of mutant strain was improved by enhancing the rate of cell increment. Since SCT-10-10-60 strain has more advantage features than current industrial strains in L-lactic acid fermentation,it is thought as a potential strain for L-lactic acid production.