Valorisation of beetroot pulp and banana plant pseudostem by a combined mild enzymatic hydrolysis to fermentable sugars and bioconversion of hydrolysates to organic acids

Do Nascimento, Rosa and Carvalheira, Mónica and Brás, Teresa and Cabral-Marques, Helena and Papaioannou, Emmanouil and Crespo, João G. and Neves, Luísa A. (2026) Valorisation of beetroot pulp and banana plant pseudostem by a combined mild enzymatic hydrolysis to fermentable sugars and bioconversion of hydrolysates to organic acids. Biomass and Bioenergy, 210: 109129. ISSN 0961-9534

Abstract

Beetroot pulp (BP) and banana plant pseudostem (PS) are abundant agricultural residues composed of lignocellulosic biomass (LB), which is rich in structural polysaccharides that can be converted to soluble sugars. However, they remain underutilized after beetroot juice production and banana fruit harvesting. Despite their widespread availability, a consistent and efficient strategy for the recovery of fermentable sugars and the subsequent fermentation of the resulting hydrolysates into value-added products is still absent. This study proposes a consolidated bioconversion route applicable to each of the BP and PS, by applying a tailored enzymatic cocktail (EC) for maximising the release of simple sugars and subsequently fermenting them to valuable organic acids. This EC, composed of cellulase, laccase, and pectinase was designed and employed for the first time to hydrolyse both LBs under comparable conditions. The enzymatic hydrolysis resulted in fermentable sugars’ recoveries of 860.53 ± 2.65 mg/g for BP and 744.82 ± 15.43 mg/g for PS, values that are equal or higher than those reported for other LBs treated enzymatically (425–776 mg/g) or by acid/base hydrolysis (114–486 mg/g). Subsequent fermentation of the simple sugars contained in the hydrolysates led to the production of acetic, butyric, and lactic acids, with concentrations of 4.04 ± 0.31 g/L and 3.91 ± 0.31 g/L for BP and PS, respectively. These results demonstrate the feasibility and applicability of the same enzymatic pre-treatment and fermentation strategy for two distinct agricultural residues, providing a practical methodology for LB valorisation and the sustainable production of organic acids relevant to industrial biotechnology and biorefinery applications.