Reutilization of green liquor chemicals for pretreatment of whole rice waste biomass and its application to 2,3-butanediol production

The performance of green liquor pretreatment using Na₂CO₃ and Na₂SO₃ and its optimization for whole rice waste biomass (RWB) was investigated. Incubation of Na₂CO₃-Na₂SO₃ at a 1:1 ratio (chemical charge 10%) for 12% RWB at 100°C for 6h resulted in maximum delignification (58.2%) with significant glucan yield (88%) and total sugar recovery (545mg/g of RWB) after enzymatic hydrolysis. Recovery and reusability of the resulting chemical spent wash were evaluated to treat RWB along with its compatibility for enzymatic digestibility. Significant hydrolysis and lignin removal were observed for up to three cycles; however, further reuse of Na₂CO₃ and Na₂SO₃ lowered their performance. Significant 2,3-butanediol (BDO) was produced by Klebsiella pneumoniae KMK-05 with the RWB enzymatic hydrolysate from each pretreatment cycle. BDO yield achieved using RWB-derived sugars was similar to those using laboratory-grade sugars. This pretreatment strategy constitutes an ecofriendly, cost-effective, and practical method for utilizing lignocellulosic biomass.