(623bk) Production of Lignocellulases by Trichoderma Viride In Free-Cell and Immobilized-Cell Fermentations: A Comparative Study of the Secretome

Abstract: Lignocellulases play an important role in the development of bioethanol. Trichoderma viride has been widely used to produce lignocellulases in submerged fermentation. However, very little is known about the effects of the fermentation conditions on lignocellulases production and secretion. In this study, production of lignocellulases and secretome of Trichoderma viride in submerged fermentations with free cells and immobilized cells in a rotating fibrous-bed bioreactor (RFBB) were investigated and compared. In general, the enzyme activities of FPase and cellobiase and the saccharification yield of sugarcane bagasse using the fermentation broth produced in the immobilized-cell fermentation were respectively 35.4%, 125.2% and 55.3% higher than those from the free-cell fermentation.  The secretomes or the protein profiles in these fermentation broths were analyzed with two-dimensional gel electrophoresis and MALDI-TOF-TOF mass spectrometry, which identified 24 protein spots with significantly different expression/secretion levels. Among them, cellobiohydrolase CBH Ⅱ (MW: 39.2 kDa, pI: 4.83), endoglucanase EG Ⅱ (MW: 44.9 kDa, pI: 4.97) and α-amylase (MW: 51.0 kDa, pI: 4.65) were highly expressed and secreted in the immobilized-cell fermentation, while free-cell fermentation gave more cellobiohydrolase CBHⅠ (MW: 47.1 kDa, pI: 4.29),  CBHⅠ (MW: 52.8 kDa, pI: 4.33), CBHⅠ (MW: 54.6 kDa, pI: 4.81), and endoglucanase EG Ⅳ (MW: 35.9 kDa, pI: 5.29). Swollenin (MW: 53.1 kDa, pI: 4.8) was also identified in both fermentations, but at different pI locations on the gel. These results suggested that different secretomes might have contributed to the higher saccharification efficiency of the fermentation broth produced in the immobilized-cell fermentation.