Mild-temperature dilute acid pretreatment for integration of first and second generation ethanol processes

•Lignocellulose integration at 1st generation ethanol plants.•Mild-temperature (100 °C) pretreatment of wheat bran, stillage fiber and saw dust.•Dilute acid pretreatment of wheat bran led up-to 300% improvement in glucose yield.•Edible fungal fermentation of pretreated stillage fiber showed 91% ethanol yield.•Proposed low energy approach of using waste-heat from 1G facility for 2G ethanol.

The use of hot-water (100 °C) from the 1st generation ethanol plants for mild-temperature lignocellulose pretreatment can possibly cut down the operational (energy) cost of 2nd generation ethanol process, in an integrated model. Dilute-sulfuric and -phosphoric acid pretreatment at 100 °C was carried out for wheat bran and whole-stillage fibers. Pretreatment time and acid type influenced the release of sugars from wheat bran, while acid-concentration was found significant for whole-stillage fibers. Pretreatment led up-to 300% improvement in the glucose yield compared to only-enzymatically treated substrates. The pretreated substrates were 191-344% and 115-300% richer in lignin and glucan, respectively. Fermentation using Neurospora intermedia, showed 81% and 91% ethanol yields from wheat bran and stillage-fibers, respectively. Sawdust proved to be a highly recalcitrant substrate for mild-temperature pretreatment with only 22% glucose yield. Both wheat bran and whole-stillage are potential substrates for pretreatment using waste heat from the 1st generation process for 2nd generation ethanol.

Graphical abstractDownload high-res image (48KB)Download full-size image