OBJECTIVE: To increase the leavening ability in the lean dough, the maltose utilization ability of baker's yeast was enhanced. METHODS: A 1.7kb PGK1 promoter and terminator were ligated and inserted into vector Yep-C to give the expression plasmid named Yep-CP. Then a 1.7kb DNA fragment containing the open reading frame and terminator of mal62 gene was amplified from Saccharomyces cerevisiae BY-14 by PCR, and inserted into Yep-CP to generate recombinant plasmid Yep-CPM. To express mal62 gene properly in S. cerevisiae, the recombinant expression plasmids Yep-CPM with copper resistance gene as the selection marker for yeast transformation were introduced into S. cerevisiae BY-14. The resulting yeast transformant BYCPM was screened on YEPD with 4 mmol/L CuSO,and identified by colony PCR. Target protein was detected by qRT-PCR, and the enzyme activities and the leavening ability of the recombinant strain BYCPM were determined to confirm whether functional expression was achieved. RESULTS: The maximum maltase activity of recombinant strain BYCPM was 15%-52% higher than that of control strain BY-C. Leavening ability and specific leavening ability of recombinant strain BYCPM were 40% and 5.6% higher than that of the control strain BY-C, respectively. CONCLUSION: The mal62-overexpression was an effective way of increasing the maltase activity and the ability of glucose depression in the baker's yeast. Moreover, recombinant strain BYCPM could further enhance the leavening ability and produce more gas while consume lesser carbon source than the control strain.
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