Produção de enzimas celulolíticas por Trichoderma reesei CCT2768 por fermentação em estado sólido usando fibra de coco verde (Cocos nucifera) pré-tratada por explosão a vapor como substrato

Abstract

The residue generated by the green coconut production chain has caused a series of environmental and public health problems, as it is a bulky organic material with slow decomposition. An alternative is its application in the processes of production of lignocellulolytic enzymes via solid state fermentation (FES), this product has been highlighted for the reduction of costs in the process of obtaining bioenergy. However, a pre-treatment step that will reduce the lignocellulose recalcitrance and the lignin and hemicellulose content in the material is necessary to increase the accessibility of fermentative microorganisms. Therefore, this study aimed to evaluate the production of cellulases using coconut fiber pretreated by steam explosion combined with alkaline pretreatment (PV+A) by FES using filamentous fungus Trichoderma reesei CCT2768. The culture conditions (water activity and amount of substrate) were evaluated through central rotational composite design (CCR), with Carboxymethylcellulase (CMCase) and Filter Paper enzyme activity (FPase) as responses. The combination of pre-treatments was more favorable for the removal of hemicellulose from green coconut fiber, reducing the content of this polymer from 10.15%, in the untreated biomass, to 5.38%, while the content of lignin increased from 21.32% to 34.82%, which may be associated with the lignin rearrangement effect during the biomass cooling process in the pretreatment. Regarding the SSF of the pretreated PV+A coconut fiber, it was observed that the solid load significantly influenced the behavior of CMCase in the cultivation, and the water activity was a significant factor in both analyzed enzymes. It could be noticed that greater production of cellulolytic enzymes occurred with water activity of 0.995 and 5.25 g of substrate, yelding an enzymatic activity of CMCases and FPases close to 3.0 IU/g and 0.31 IU/g, respectively. The saline solution of 154 mM NaCl was more efficient in the recovery of the enzymes, producing an extract with the activity of 5.19 IU/g for endoglucanase and 1.19 IU/g for the FPase. Therefore, the best conditions of water activity and solid loading for the cellulases production were identified and significant values of CMCase and FPase activities are found. The study contributes to the construction of a new production chain for the use of green coconut husk through the production of lignocellulolytic enzymes from FES of lignocellulosic biomass pre-treated by steam combined with alkaline.