Produção de biossurfactante por Rhodotorula mucilaginosa em hidrolisado hemicelulósico do bagaço de malte

Abstract

The residues from agro-industries are rich in carbohydrates and are currently being studied for the production of several value-added products (biosurfactants, biogas, ethanol, xylitol, amino acids, vitamins, enzymes, biocomposites, etc.). The reuse of waste is an ecologically viable alternative, as it contributes to reducing the pollution of the environment and valuing these, coming from agribusiness. Among these residues, malt bagasse (BM) stands out, which is a lignocellulosic residue from the brewing agribusinesses, produced on a large scale throughout the world. This residue is mainly destined as animal feed; however, the offer exceeds the demand. Thus, it is necessary to search for new alternatives for the reuse of the BM. Some studies report that BM can be used as a supplement in the human diet due to its high fiber and protein content, and it is also widely studied for the production of ethanol and xylitol. However, in the literature there are no reports on the production of biosurfactant from this residue. Thus, the main focus of this research was to study the potential of BM for biosurfactant production by the oleaginous yeast Rhodotorula mucilaginosa LBP5. From the physical-chemical characterization of BM, it was found that this biomass is rich in fibers, proteins, minerals and sugars. And for BM to be used in the fermentation process, its hydrolysis with dilute acid (1.6% H2SO4) was necessary to release the fermentable sugars present in the hemicellulose structure. The obtained hemicellulosic hydrolysates were used as carbon source by R. mucilaginosa LBP5 during the production of biosurfactant. The biosurfactant produced was anionic in nature, and through the FT-IR technique it can be inferred that it is of the glycolipids type, which has a Critical Micellar Concentration of 1.5 g/L, reduces the surface tension to 40,7 mN/m. Furthermore, it presented emulsifying properties (I.E% = 72%) and stability under extreme conditions such as temperature (4 – 80 ºC), pH (4-10) and salinity (2 – 8% NaCl). Thus, the BM hydrolyzate can be used as an alternative carbon source for the production of biosurfactant from yeast.