AUTHOR=Guo Wenzhu , Liu Dandan , Li Jingen , Sun Wenliang , Sun Tao , Wang Xingji , Wang Kefen , Liu Qian , Tian Chaoguang 

TITLE=Manipulation of an α-glucosidase in the industrial glucoamylase-producing Aspergillus niger strain O1 to decrease non-fermentable sugars production and increase glucoamylase activity

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1029361

DOI=10.3389/fmicb.2022.1029361

ISSN=1664-302X

ABSTRACT=<p>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 <italic>Aspergillus niger</italic> O1. The results showed the transglycosylation product panose was decreased by more than 88.0% in <italic>agdA</italic>/<italic>agdB</italic> 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 Δ<italic>A</italic>Δ<italic>B</italic>-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.</p>