研究了中性海藻糖酶基因（NTH1和NTH2）对面包酵母耐冷冻性的影响。通过分析中性海藻糖酶基因缺失突变株和亲本菌株(BY6-9α)的生长曲线、生物量、比生长速率、中性海藻糖酶酶活力、胞内海藻糖含量、胞内海藻糖降解速率、冷冻存活率、冷冻前产气量、比发酵力、冷冻后产气量和相对发酵力，结果表明，中性海藻糖酶基因对酵母生物量、比生长速率、胞内海藻糖含量和比发酵力均无显著影响，而相对于亲本菌株(BY6-9α)，TL-101(nth1△)和TL-201(nth1△nth2△)的胞内海藻糖降解速率分别减慢了9.22%和15.60%，冷冻后CO2产生量分别提高了63.04%和65.22%，-20 ℃冷冻28 d后冷冻存活率分别提高了91.06%和103.01%，冷冻后相对发酵力分别提高了95.95%和116.04%，这充分说明敲除NTH1基因能明显改善酵母菌株的耐冷冻特性，而且酵母的耐冷冻特性与胞内海藻糖降解速率呈负相关。TL-102(nth2△)的耐冷冻特性与亲本菌株无显著差异，说明单敲NTH2基因对酵母耐冷冻性无显著影响。

The effect of neutral trehalase genes deletion on the bread yeast was investigated by analysis of the growth curve, biomass, specific growth rate, neutral trehalase activity, intracellular trehalose content, degradation speed of intracellular trehalose, survival ratio, specific fermentation ability, CO2 production before and after freezing, and the relative fermentation ability after freezing of trehalase genes deletion mutants and the parental strain (BY6-9α). It was found that the trehalase genes had less significant effects on biomass, specific growth rate, intracellular trehalose content and the specific fermentation ability of bread yeast. The degradation speed of intracellular trehalose of TL-101(nth1△)and TL-201(nth1△nth2△) was 9.22% and 15.60% lower than the parental strain respectively. Meanwhile, the CO2 production after freezing of TL-101 and TL-201 increased 63.04% and 65.22% compared with the parental strain. Furthermore, the survival ratio of TL-101 and TL-201 after freezing for 28 days at -20 ℃ was 91.06% and 103.01%, respectively, higher than the parental strain, and the relative fermentation ability after freezing was 95.95% and 116.04% higher than the parental strain, respectively. These results revealed that deletion of NTH1 gene sufficiently improved the freeze-tolerance characteristics of bread yeast, and there was a negative correlation between the degradation speed of intracellular trehalose and freeze-tolerance characteristics of bread yeast. On the other hand, the freeze-tolerant characteristics of TL-102(nth2△) were not significant difference as that of the parental strain, which indicated that single NTH2-deleted was not significantly influence on the freeze-tolerant characteristics of bread yeast.

国家自然科学基金资助项目（31171730）；国家高技术研究发展计划（863计划）（2013AA102106）；教育部“长江学者和创新团队发展计划”（IRT1166）