Remediation of sugarcane vinasse using Rhodotorula glutinis or Rhodotorula mucilaginosa: Biomass morphology and its potential technological applications

Abstract

There is an emerging interest of use biological processes for vinasse treatment generally because they are able to produce interesting metabolites from living cells. Additionally, the production of yeasts with weakened cell wall without modifying its physiological performance would be of great technological value not only to facilitate the extraction of intracellular metabolites but also to increase the biomass digestibility. This study explored the remediation of a glycerol-fortified sugarcane vinasse using Rhodotorula glutinis or Rhodotorula mucilaginosa coupled with the production of valuable residual biomasses displaying a tailor-made weakened cell wall. Firstly, the biomass-bound ß-d-glucosidase activity was selected as a proper cell wall lytic potential marker. Secondly, in vitro-dose response assays with several metal ions showed that the presence of 6 mM of MnCl2 and FeCl3 increased the ß-d-glucosidase activity in R. glutinis and R. mucilaginosa, respectively. Thirdly, the supplementation of those salts to either YPD or vinasse-based media was evaluated. As a result, cells were bigger or even rounder than the corresponding controls (without metal ions supplementation) suggesting a weakening of the cell wall. Finally, as proof of concept, after 6 days of vinasse treatment at 30 °C under stirred conditions, the reduction of COD value for R. glutinis and R. mucilaginosa was 81.3% and 80.8%, respectively. The final biomass, lipid and protein concentrations for R. glutinis were 15.1 g/L, 31.1% and 48.12%, respectively. The final biomass, lipid and protein concentrations for R. mucilaginosa were 15.7 g/L, 31.5% and 48.12%, respectively. Potential technological applications of residual biomass were also discussed.