Paper mill sludge rich enzymes and microbial community promotes the hydrogenesis of black liquor containing furfural.

Black liquor (BL) bioconversion into valuable by-products is essential to develop a bioeconomy strategy; however, its furfural content hinders microbial fermentation activities. Hence, this study utilizes paper mill sludge (PMS) to provide extracellular enzymes, furfural-degrading microbial consortia, and electron donor required for promoting the BL hydrogenesis potential. Three up-flow anaerobic sequential batch reactors (UASBRs) are fed with PMS (UASBR1), BL (UASBR2), and PMS + BL (UASBR3) and operated in parallel at 15 min fill, 72 h reaction, and 4 h settling. The UASBR3 achieves the maximum volumetric H 2 of 1.483 ± 0.088 L/L/d and H 2 yield of 2.06 ± 0.12 mol/mol glucose, which drops by 88% in UASBR2 and 24% in UASBR1. The insufficient H 2 productivity values in UASBR2 could be due to a lack of nutrients availability (C:N = 440:1 and C:P = 19:1), higher furfural concentration (2116 ± 422 mg/L), and involvement of the butyrate fermentation pathway. The synergetic effect between PMS and BL overcomes these limitations and enriches the fermentation medium with Proteobacteria phyla (22.8%) and Acinetobacter sp. degrading furfural (6.1%). The microbial community at the phylum level (e.g., Proteobacteria , Firmicutes , and Actinobacteria) in UASBR3 maximizes the migration of electrons (e−eq = 9.34 ± 0.54%) towards efficient H 2 formation. [Display omitted] • Paper mill sludge (PMS) mitigated inhibitory effect of furfural in black liquor (BL). • PMS improved H 2 yield from the BL by 8.3-folds and accounted for 2.1 mol/mol glucose. • e– eq transferred to H 2 was 9.3% in the PMS:BL, 7.4% in PMS, and 1.27% in BL. • Acinetobacter degrading furfural (6.1%) was abundant with PMS addition. • Bacilli (8.9%) and Clostridia (5.4%) was dominant in the hydrogenesis of PMS:BL. [ABSTRACT FROM AUTHOR]