Tian Junjie, Wei Shumin, Liang Wenxing, Wang Guangyuan
College of Life Sciences, Shandong Province Key Laboratory of Applied Mycology, Qingdao Agricultural University, Changcheng Road, No.700, Qingdao, 266109, China.
College of Plant Health and Medicine, The Key Laboratory of Integrated Crop Pest Management of Shandong Province, Qingdao Agricultural University, Qingdao, 266109, China.
Synth Syst Biotechnol. 2024 Aug 20;10(1):68-75. doi: 10.1016/j.synbio.2024.08.005. eCollection 2025.
Levan produced by spp. has great potential in biotechnological applications. However, spp. can synthesize organic acids during fermentation, resulting in environmental acidification. Few studies have focused on the effects of environmental acidification on levan synthesis. This study revealed that the organic acids, mainly gluconic acid (GA) and 2-keto-gluconic acid (2KGA) secreted by sp. MP2116 created a highly acidic environment (pH < 3) that inhibited levan biosynthesis. The levansucrase derived from strain MP2116 had high enzyme activity at pH 4.0 ∼ pH 6.5. When the ambient pH was less than 3, the enzyme activity decreased by 67 %. Knocking out the gene of membrane-bound glucose dehydrogenase (mGDH) in the GA and 2KGA synthesis pathway in strain MP2116 eliminated the inhibitory effect of high acid levels on levansucrase function. As a result, the levan yield increased from 7.4 g/l (wild-type) to 18.8 g/l (Δ) during fermentation without pH control. This study provides a new strategy for improving levan production by preventing the inhibition of polysaccharide synthesis by environmental acidification.
由 属产生的果聚糖在生物技术应用中具有巨大潜力。然而， 属在发酵过程中会合成有机酸，导致环境酸化。很少有研究关注环境酸化对果聚糖合成的影响。本研究表明， 属MP2116分泌的有机酸，主要是葡萄糖酸（GA）和2-酮葡萄糖酸（2KGA），创造了一个高酸性环境（pH < 3），抑制了果聚糖的生物合成。源自菌株MP2116的果聚糖蔗糖酶在pH 4.0至pH 6.5时具有高酶活性。当环境pH小于3时，酶活性下降67%。敲除菌株MP2116中GA和2KGA合成途径中膜结合葡萄糖脱氢酶（mGDH）的基因，消除了高酸水平对果聚糖蔗糖酶功能的抑制作用。结果，在无pH控制的发酵过程中，果聚糖产量从7.4 g/l（野生型）增加到18.8 g/l（Δ）。本研究提供了一种新策略，通过防止环境酸化对多糖合成的抑制来提高果聚糖产量。
