Production of Enzymes from Rice Husks and Wheat Straw in Solid State Fermentation

In Europe, the agricultural wastes represent a significant potential for the development of biorefineries in different sectors such as cereals. Recovery of phytochemicals as well as the energetic valorization of the plant matrixes needs the demolition of the wall cell plants. Hydrolitic demolition by lignocellulosic enzymes is one of the most studied approach. White rot fungi such as Pleurotus ostreatus produce a wide range of extracellular enzymes to degrade complex lignocellulosic substrates into soluble substances that can be used as nutrients. The objective of this study is to induce the production of lignocellulosic enzymes through the growth Pleurotus ostreatus in solid state fermentation using agro-food wastes as substrates: rice husks and wheat straw. The activities of cellulase, xylanase, peroxidase, laccase, and arylesterase are determinate by specific colorimetric assays. All trials showed a scarce productivity of cellulase while all the detected enzymatic activities resulted higher using rice husk as a substrate than in presence of wheat straw. Pleurotus ostreatus exhibited a prevalent production of arylesterase activity and, in particular, the contemporary presence of significant xylanase and feruloilesterase activities was probably due to the typical ferulic bond and diferulic bridge in the heteroxylane structure of monocot's plant cell walls such as rice and wheat. Moreover, in terms of yields arylesterase activities for both substrates, are prevalent on other activities. Our findings showed that the enzymatic production was strictly dependent to the periodic removal of the produced enzymes. The development of new solid state bioreactor design for a steady state production of enzymes from Pleurotus ostreatus could open an interesting industrial approach.