Two-stage co-hydrolysis of rice straw by Trichoderma reesei ZM4-F3 and Pseudomonas aeruginosa BSZ-07

Rhamnolipid biosurfactant was added to rice straw hydrolysis system to enhance the production of reducing sugars. Differing from the traditional method, on-site production of rhamnolipid made the rice straw decomposing fungus Trichoderma reesei ZM4-F3 and rhamnolipid producing bacteria Pseudomonas aeruginosa BSZ-07 work together. As the growth periods of these two strains are 96 h and 48 h, respectively, a new two-stage co-hydrolysis bioprocess was achieved. T. reesei ZM4-F3 was cultivated for rice straw hydrolysis in the first 48 h at suitable conditions. For the next 48 h, the results showed that the temperature of 34 °C and pH value of 5.5 were the optimum conditions, and the optimum adding inoculation concentration ratio of P. aeruginosa BSZ-07 to T. reesei ZM4-F3 was 4%. Under these conditions, the co-hydrolysis sample could improve the production of reducing sugars to 2.57 g l−1, 15.20% higher than that of the control. The increased enzyme stability was indicated to be one of the mechanisms of the stimulatory effect of rhamnolipid on rice straw hydrolysis system. Compared with Tween-80 and sodium dodecylsulphate, rhamnolipid biosurfactant exhibited a better stimulatory effect on rice straw hydrolysis. Since the two-stage co-hydrolysis system could leave out the rhamnolipid purification process, thus reducing the biosurfactant production cost effectively, it seems to be a new prospective bioprocess for rice straw hydrolysis.