Effects of different cellulases on the release of phenolic acids from rice straw during saccharification

•Phenolic acids released in different forms from rice straw during saccharification.•Synergistic interaction between FAE and cellulase increased free phenolic acids.•Synergistic interaction affected ABTS and DPPH capacities of phenolic acids.•Phenolic acids can be produced as value-added products from rice straw.•Co-production technology is an attractive process for ethanol and phenolic acids. Effects of different cellulases on the release of phenolic acids from rice straw during saccharification were investigated in this study. All cellulases tested increased the contents of phenolic acids during saccharification. However, few free phenolic acids were detected, as they were present in conjugated form after saccharification when the cellulases from Trichoderma reesei, Trichoderma viride and Aspergillus niger were used. On the other hand, phenolic acids were present in free form when the Acremonium cellulolyticus cellulase was used. Assays of enzyme activity showed that, besides high cellulase activity, the A. cellulolyticus cellulase exhibited high feruloyl esterase (FAE) activity. A synergistic interaction between FAE and cellulase led to the increase in free phenolic acids, and thus an increase in antioxidative and antiradical activities of the phenolic acids. Moreover, a cost estimation demonstrated the feasibility of phenolic acids as value-added products to reduce the total production cost of ethanol.