Optimization of Enzyme Production from Streptomyces by Solid-state Fermentation of Agricultural Wastes using the Orthogonal Projections to Latent Structures-Discriminant Analysis (OPLS-DA) Method

Abstract This study used Orthogonal Projections to Latent Structures-Discriminant Analysis (OPLS-DA) to identify and optimize the combined effect of the temperature, fermentation time, substrate-type, and fermenting microorganism on solid-state fermentation (SSF) culture of different agricultural wastes, in order to evidence the interactions among variables that allow maximizing the production of each enzyme. Thus, barley and wheat straw were fermented using two Streptomyces strains (S. MDG 301 and S. MDG 147) under SSF conditions. Key degradative enzymes (xylanases, carboxylmethilcellulase (CMCase), mannanase, laccase and peroxidase) and lignin solubilisation were evaluated. Our results highlighted that the highest xylanases and CMCase levels were obtained after treatment of wheat straw for two days with the S. MDG 301 strain at 45°C. Similarly, we found that the highest mannanase level was achieved using the S. MDG 147 strain on the barley straw at 28°C. Therefore, the integrated approach used based on analytical and bio statistical methods, proved to be a valuable tool for an accurate and rapid determination of the most significant parameters for controlling the bio-transformation process in terms of the enzymatic activity and lignin solubilisation.