Biorefinery based on discarded red beetroot: production of bioactive compounds and 2,3-butanediol

Abstract

Discarded red beetroot (DRB) is an organic waste produced in the food processing industry, rich in phytochemicals and sugars. This study compares biorefinery schemes for the valorisation of DRB. Two different alternatives were compared to select the most favourable considering global yields and production costs. In scenario 1 (multi-product biorefinery), 0.9 g of phenolics and 0.8 g of betalains were recovered from 100 g of DRB (on dry basis). After extraction, the solid fraction was fed to enzymatic hydrolysis and fermentation to obtain 2,3-butanediol (2,3-BDO) with Paenibacillus polymyxa, achieving a global yield of 9.3 g/100 g DRB. In scenario 2, all the DRB was subjected to enzymatic hydrolysis and subsequent fermenta- tion with P. polymyxa, obtaining a 2,3-BDO global yield of 25.5 g from 100 g DRB. The economic evaluation indicated that a multi-product biorefinery could be the most cost-effective alternative for DRB valorisation, leading to minimum selling prices competitive with the petrochemical route. Thus, the potential for the efficient use of DRB in an integrated biorefinery for the production of high value-added products was demonstrated.