Heterologous expression of small heat shock protein by Oenococcus oeni improves its ethanol tolerance

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Small heat shock proteins (sHsps) promote microbial resistance to harsh environmental conditions. Three sHsp genes (lphsp) from Lactobacillus plantarum and one (lohsp) from Oenococcus oeni were cloned and transformed into Lactococcus lactis MG1363, which does not contain sHSPs for heterologous expression. Comparing the tolerance of different recombinant strains to ethanol, the lphsp19.3 gene with the highest tolerance was selected and inserted into the expression vector pHH40 and transformed into the new host O. oeni. The results showed that when compared with the ethanol tolerance of the original O. oeni strain, i.e., 12% v/v, the recombinant strain could tolerate approximately 14% v/v. Moreover, the recombinant strain shortened the malo-lactic fermentation time of wine by 2 days without any adverse effects on aroma. Therefore, the recombinant O. oeni strain showed better application prospects.