Production of R -2-(4-Hydroxyphenoxy) Propionic Acid from Corncob Hydrolysate by Beauveria bassiana through a Biofilm-Based Fermentation Strategy

Corncob, rich in cellulose and hemicellulose, is a promising feedstock for fermentable sugar production. This study aimed to optimize the release of reducing sugars and the biosynthesis of R-2-(4-hydroxyphenoxy) propionic acid (R-HPPA) from corncob hydrolysate (CCH) using a biofilm-based fermentation strategy with Beauveria bassiana. Dilute acid pretreatment (2.4% H2SO4, 121 °C, 29 min) yielded 38.2 g/L reducing sugars (CCH-1). Detoxification with Ca(OH)2 and activated carbon effectively removed 99.0% furfural and 99.2% 5-hydroxymethylfurfural, with less than 10% sugar loss (CCH-3). To enhance R-HPPA production, different CCH hydrolysates were evaluated: CCH-2 (CCH-1 treated with Ca(OH)2), CCH-3 (CCH-1 treated with Ca(OH)2 and activated carbon), and CCH-4 (CCH-3 concentrated to varying reducing sugar concentrations). The highest R-HPPA titer (15.9 g/L) was achieved when the hydrolysate was neutralized, detoxified, and concentrated to 60 g/L reducing sugars. This process highlights the potential of CCH as a low-cost and renewable substrate for industrial R-HPPA production.