Biosorption of Phenolic Compounds in Lignocellulosic Biomass Biorefineries

The phenolic compounds released during the pretreatment of lignocellulosic biomass negatively affect the saccharification and alcoholic fermentation process. Therefore, the development of strategies to minimize the negative impact of the released inhibitory compounds is key to improve the overall yield and techno-economic viability of future biorefineries. This work proposes the use of Aspergillus niger biomass as a low-cost biosorbent for removal of the phenolics released during liquid hot water (LHW) pretreatment of sugarcane bagasse. Such approach would be advantageous given that fungal microbial biomass could be readily available in biorefineries, as a co-product of the in-house production of cellulolytic enzymes. Three types of A. niger biomass powders were used for adsorption of vanillin (monomer), tannic acid (oligomer), and total phenolics from the LHW pretreatment liquor. A 98% removal of tannic acid was obtained by the biosorbent treated with sodium hydroxide, while adsorption of vanillin was lower, with removal of around 30%. Removal of around 40% was obtained for the total phenolics present in the LHW pretreatment liquor, resulting in a remarkable 50% increase of glucose release in the saccharification of sugarcane bagasse. These findings showed the potential of using the fungal biomass as cost-effective biosorbents for removing the inhibitors released in the pretreatment process and improving the conversion efficiency in biorefineries.