Efficient one-pot lactic acid production from cellulose via a Trichoderma reesei and Bacillus coagulans cooperation leveraging substrate-induced secretomes.
The high cost of cellulase production presents a major bottleneck in lignocellulosic biorefining. Herein, we investigated the role of secretomes induced by different substrates in mediating the synergistic interplay of Trichoderma reesei (T. reesei) and Bacillus coagulans (B. coagulans) for efficient lactic acid production. Substrate crystallinity directly affects the expression levels and enzymatic profiles in T. reesei, thereby influencing its hydrolytic performance. High-crystalline substrate induced a more balanced cellulase system, whereas low-crystallinity substrate favored the production of a β-glucosidase-enriched cocktail. This "substrate-enzyme-function" relationship was leveraged to construct a CBP system in which B. coagulans compensates for the intrinsic β-glucosidase deficiency of T. reesei through its efficient cellobiose metabolism. The synergistic cooperation achieved a near-theoretical lactic acid yield of 96.41% from cellulose without external enzyme supplementation. This work provides an induction-based strategy for designing efficient microbial consortia and offers insights for improving the efficiency and sustainability of lignocellulosic biorefining.