Identification and Screening of β-glucanase-producing, Salt-tolerant Zygosaccharomyces rouxii
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Abstract:
A salt-tolerant yeast strain was isolated and purified from a homemade chili sauce. Congo red agar plate method confirmed that the strain produced extracellular β-1,3-glucanase. The NaCl-tolerance test showed that the strain had high salt-tolerance, with stable growth observed for 120 h in medium B containing 24% NaCl after an adaptation period of 144 h. The strain was identified as Zygosaccharomyces rouxii A via 26S rRNA sequence analysis. Secondary growth phenomenawere observed during fermentation where the biomass reached peak values at 24 and 48 h, with an increase of 46.55% (9.35 g/L) and 87.15% (11.94 g/L), respectively, compared with that at 18 h (6.38 g/L). However, the glucose concentration remained constant at 1.57 g/L after 21 h. The results indicated that the β-1,3-glucanase produced by Z. rouxii A degraded the 1,3-1,6-glucan present in the substrate, thus providing carbon and energy sources for the secondary growth of cells. Additionally, β-1,3-glucanase activity curve was consistent with the growth curve for Z. rouxii A, which showed that maximum enzyme activity rapidly decreased with cell autolysis (12, 24, and 48 h), and peak enzyme activity level (15.23 U/mL) was reached at 48 h. The results suggest that β-1,3-glucanase synthesis was coupled with cell growth and that the strain could produce this enzyme in the presence of high salt concentration.
