耐高渗克鲁斯假丝酵母的耐受性

Tolerance of hyperosmolar Candida krusei

摘要:

利用工业微生物将木质纤维素转化为具有高附加值的化工原料，是实现碳中和及可持续生物经济的重要途径。经预处理的木质纤维素酶解液中往往含有糖、盐、酚/醛等多种物质，直接发酵需要微生物有较强的耐受性。本文通过考察克鲁斯假丝酵母(Candida krusei)对底物、盐、高温冲击的耐受性，进一步验证耐高渗假丝酵母直接利用海水中预处理的巨菌草(Pennisetum sinese grasses)酶解液进行发酵的可能性。结果表明，适应性驯化的克鲁斯假丝酵母可以耐受200 g/L的葡萄糖，具有耐受高渗的能力；用海水替代淡水、不灭菌发酵的甘油产量较淡水灭菌发酵提高了109%；发酵32 h时热冲击结合48 h时引入10 g/L亚硫酸钠，葡萄糖转化为甘油的产率为0.37 g/g，比对照组提升了225%；用海水中预处理的巨菌草酶解液发酵，葡萄糖生成甘油及乙醇的总转化率可达0.45 g/g。耐高渗克鲁斯假丝酵母对底物、盐、温度表现出较强的适应性，不仅能直接利用复杂的木质纤维素酶解液，还对其表现出较强的耐受性，为利用木质纤维素生产生物基化学品提供了候选菌株。

Abstract:

The utilization of industrial microorganisms for the conversion of lignocellulose into high value-added chemicals is an essential pathway towards achieving carbon neutrality and promoting sustainable bioeconomy. However, the pretreated lignocellulase hydrolysate often contains various sugars, salts, phenols/aldehydes and other substances, which requires microorganisms to possess strong tolerance for direct fermentation. This study aims to investigate the tolerance of Candida krusei to substrate, salt, and high temperature shock, in order to validate its potential for utilizing the enzymatic hydrolysate of Pennisetum giganteum in seawater for fermentation. The experimental results showed that the adaptively domesticated C. krusei exhibited tolerance to glucose at a concentration of 200 g/L and became a hypertonic strain. When seawater was used instead of freshwater without sterilization, the yield of glycerol in fermentation was 109% higher than that in freshwater with sterilization. Moreover, the combined thermal shock at 32 hours of fermentation and addition of 10 Na₂SO₃ at 48 hours resulted in a yield of glycerol to glucose 0.37 g/g, which was 225% higher than the control group. By fermenting the enzymatic hydrolysate of P. giganteum pretreated in seawater, the total conversion rate of glucose into glycerol and ethanol reached 0.45 g/g. This study indicates that hypertonic C. krusei exhibits remarkable adaptability to substrate, salt, and temperature. It not only can directly utilize complex lignocellulosic hydrolysates, but also exhibits strong tolerance to them. Therefore, it provides a potential candidate strain for the production of bio-based chemicals using lignocellulosic processes.