Guo Wenzhu, Liu Dandan, Li Jingen, Sun Wenliang, Sun Tao, Wang Xingji, Wang Kefen, Liu Qian, Tian Chaoguang
Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.
National Technology Innovation Center of Synthetic Biology, Tianjin, China.
Front Microbiol. 2022 Oct 20;13:1029361. doi: 10.3389/fmicb.2022.1029361. eCollection 2022.
Dextrose equivalent of glucose from starch hydrolysis is a critical index for starch-hydrolysis industry. Improving glucose yield and decreasing the non]-fermentable sugars which caused by transglycosylation activity of the enzymes during the starch saccharification is an important direction. In this study, we identified two key α-glucosidases responsible for producing non-fermentable sugars in an industrial glucoamylase-producing strain O1. The results showed the transglycosylation product panose was decreased by more than 88.0% in / double knock-out strains than strain O1. Additionally, the B-P1 domain of agdB was found accountable as starch hydrolysis activity only, and B-P1 overexpression in ΔΔ-21 significantly increased glucoamylase activity whereas keeping the glucoamylase cocktail low transglycosylation activity. The total amounts of the transglycosylation products isomaltose and panose were significantly decreased in final strain B-P1-3 by 40.7% and 44.5%, respectively. The application of engineered strains will decrease the cost and add the value of product for starch biorefinery.
淀粉水解所得葡萄糖的葡萄糖当量是淀粉水解工业的关键指标。提高葡萄糖产量并减少淀粉糖化过程中由酶的转糖基化活性产生的非发酵性糖是一个重要方向。在本研究中，我们鉴定出了在工业产糖化酶菌株O1中负责产生非发酵性糖的两种关键α-葡萄糖苷酶。结果表明，与菌株O1相比，双敲除菌株中的转糖基化产物帕拉金糖减少了88.0%以上。此外，发现agdB的B-P1结构域仅具有淀粉水解活性，在ΔΔ-21中过表达B-P1可显著提高糖化酶活性，同时保持糖化酶混合物的低转糖基化活性。最终菌株B-P1-3中转糖基化产物异麦芽糖和帕拉金糖的总量分别显著降低了40.7%和44.5%。工程菌株的应用将降低淀粉生物精炼的成本并增加产品价值。
