Biopigments production from sugarcane bagasse hemicellulosic hydrolysate using cells of Monascus ruber immobilized in polyurethane foam.

Abstract

The complete use of all fractions of agro-industrial by-products is essential to promote sustainability and consolidated bioprocesses in biorefineries. Among the biomass fractions, hemicellulose is still underutilized and could be used to produce high value bioproducts, as fungal biopigments, emerging biomolecules with potential applications in different industrial sectors. Besides raw material, cultivation strategies such as the use of immobilized cells can be interesting for industrial applications, presenting advantages by favoring downstream steps and reuse of cells in repeated or continuous bioprocesses. In this study, the production of biopigments by Monascus ruber immobilized in polyurethane foam was evaluated as a strategy to valorize a xylose-rich sugarcane bagasse hemicellulosic hydrolysate. An experimental design was carried out and showed the optimum xylose/glucose ratio obtained was similar to the values usually found in sugarcane bagasse hemicellulosic hydrolysates. Then, the kinetic profile of the in situ immobilization of the fungus (simultaneous cell growth and adsorption) in polyurethane indicated an inoculum preparation time of 8 days of growth/immobilization before the process conducted in hydrolysate-based medium. The use of immobilized cells resulted in the production of biopigments with maximum values of 13.1 AU, 11.87 AU, and 11.32 AU of yellow, orange and red biopigments, respectively, in medium based on detoxified hydrolysate. The obtained results can contribute to the valorization of agro-industrial by-products as an alternative source of substrates, as well as to future research to explore the potential of immobilizing filamentous fungi in bioprocesses, such as the reuse of cells and continuous systems for production of biopigments.