Rapid adaptive evolution of Bacillus coagulans to undetoxified corncob hydrolysates for lactic acid production and new insights into its high phenolic degradation

Here, an adapted Bacillus coagulans (Weizmannia coagulans) strain CC17B-1 was developed for lignocellulosic lactic acid production through a short and rapid adaptive laboratory evolution technique. Without any detoxification, two actual corn cob hydrolysates from the factory were effectively fermented to lactic acid within 60 h. Strain CC17B-1 is capable of degrading all nine determined phenolic compounds in the hydrolysate, with the only exception being vanillic acid. Notably, its tolerances for ferulic acid and p-coumaric acid are the highest doses reported in anaerobic microbes. A proposed degradation pathway showed that strain CC17B-1 could convert phenolic aldehydes to phenolic alcohol and then further degrade them completely. This work provides new ideas for the microbe phenolic degradation pathway and paves the way for industrial lactic acid production from lignocellulosic biomass.

Automated summary

An adapted Bacillus coagulans strain was developed for lactic acid production from lignocellulosic biomass. Without detoxification, actual corn cob hydrolysates were effectively fermented to lactic acid within 60 hours. The strain was capable of degrading nine phenolic compounds, except for vanillic acid, with the highest tolerance reported for ferulic acid and p-coumaric acid in anaerobic microbes. A proposed degradation pathway showed the conversion of phenolic aldehydes to phenolic alcohol and their complete degradation. This work provides insights into the microbe phenolic degradation pathway and enables industrial lactic acid production from lignocellulosic biomass.