Stimulatory effect of in-situ detoxification on bioethanol production by rice straw

An effective ferulic acid degrading bacterium, Escherichia sp. HHQ-1, was added to alkali-pretreated rice straw degrading system to in-situ detoxify the ferulic acid inhibitors existed in the hydrolysates. It was shown that the production of reducing sugars in Escherichia sp. HHQ-1-Trichoderma reesei consortia degrading system could achieve 221.33 mg L⁻¹ at 60 h, which was 7.84% higher than that in single degrading system. All the three main cellulases were more stable in consortia degrading system, and the activity of β-glucosidase was 4.23 fold higher than that in single degrading system. Besides, it was supposed that cell membrane was more integrally protected in consortia degrading system. Scanning Electron Microscope (SEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectrometer (FTIR) were used to observe the morphological changes of rice straw biomass. It was indicated that in-situ detoxification could severely destroy basic tissue of rice straw, dramatically decrease crystallinity index of crystalline region and effectively degrade refractory-degraded lignin parts of lignocellulose. Compared to the single degrading system, the consortia degrading system could in-situ detoxify the main inhibitors which existed in pretreated rice straw hydrolysates, realize simultaneous pretreatment and detoxification, thus increasing the bioethanol yield and reducing the cost of bioethanol production.