Synergistic effects of multiple enzymes from industrial Aspergillus niger strain O1 on starch saccharification

Background: Starch is one of the most important renewable polysaccharides in nature for production of bio-ethanol. The starch saccharification step facilitates the depolymerization of starch to yield glucose for biofuels production. The filamentous fungus Aspergillus niger (A. niger) is the most used microbial cell factory for production of the commercial glucoamylase. However, the role of each component in glucoamylases cocktail of A. niger O1 for starch saccharification remains unclear except glucoamylase. Results: In this study, we identified the key enzymes contributing to the starch saccharification process are glucoamylase, alpha-amylase and acid alpha-amylase out of 29 glycoside hydrolases from the 6-day fermentation products of A. niger O1. Through the synergistic study of the multienzymes for the starch saccharification in vitro, we found that increasing the amount of alpha-amylase by 5-10 times enhanced the efficiency of starch saccharification by 14.2-23.2%. Overexpression of acid alpha-amylase in strain O1 in vivo increased the total glucoamylase activity of O1 cultures by 15.0%. Conclusions: Our study clarifies the synergistic effects among the components of glucoamylases cocktail, and provides an effective approach to optimize the profile of saccharifying enzymes of strain O1 for improving the total glucoamylase activity.

Automated summary

This study identified key enzymes involved in the starch saccharification process, including glucoamylase, alpha-amylase, and acid alpha-amylase, out of 29 glycoside hydrolases from the 6-day fermentation products of A. niger O1. Synergistic effects were observed among the components of glucoamylases cocktail, with an increase in alpha-amylase leading to improved efficiency of starch saccharification. Overexpression of acid alpha-amylase in strain O1 resulted in an increase in total glucoamylase activity.