Multi enzyme production from mixed untreated agricultural residues applied in enzymatic saccharification of lignocellulosic biomass for biofuel

• Published in: Process safety and environmental protection 2024-06, Vol.186, p.540-551
• Main Authors: Tunio, Azhar Ali, Naqvi, Muhammad, Qureshi, Abdul Sattar, Khushk, Imrana, Jatt, Abdul Nabi, Nizami, Abdul-Sattar, Naqvi, Habib Ahmed, Charan, Tanzeel Rehman, Bhutto, Miher Ali, Tunio, Nazir Ahmed, Qamer-u-Nisa
• Format: Article
• Language: English
• Subjects: Agricultural waste; Bioethanol; Ionic liquid tolerant bacteria; Multi enzyme production; Single vessel operation through pretreatment to fermentation
• ISSN: 0957-5820; 1744-3598
• DOI: 10.1016/j.psep.2024.04.039

Lignocellulose recalcitrance essentially dictates high cost and low efficiency of its enzymatic saccharification. The complex lignocellulosic structure is a major obstacle to enzymatic saccharification and green ionic liquid pretreatment methods face difficulty of water washing prior enzymatic hydrolysis. Ionic liquid tolerant lignocellulolytic enzymes overcome the inhibition of enzymes during enzymatic saccharification and eliminated water washing step after pretreatment of lignocellulosic biomass. The cell wall composition cellulose, hemicellulose, and lignin, three main wall polymers of various agricultural residues and food waste lignocellulose substrates also affected the enzyme activities secreted by the B. subtilis strain. This study explores the potential of the halophilic, alkalophilic, and ionic liquid (IL)-tolerant strain Bacillus subtilis BC-001 for the simultaneous production of hydrolytic enzymes essential for lignocellulosic bio-refinery processes. BC-001 produced cellulase, amylase, xylanase, pectinase and protease are 70.41, 87.14, 65.50, 122.55 and 66.48 U/mL, respectively under optimized fermentation conditions. Cellulase produced by BC-001 retained more than 80% activity after 72 hours in 20% w/w of different ILs tested and enzymes retained more than 68% activities after 12 h in 50% w/w ILs. Employing such IL-stable cellulase, enzymatic saccharification is conducted without water washing on rice straw (RS) that has been pretreated with various ILs, including 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and choline chloride. This research is novel as the study marks the first instance of multi-hydrolytic enzyme production from a novel alkalophilic, halophilic, thermophilic, and IL-tolerant bacterial strain using a mixture of untreated agricultural residues. [Display omitted] •Halophilic bacterial strain is isolated from saltern soil.•Multi hydrolytic enzymes are produced from untreated biomass.•Bacterial strain tolerated 12% w/w of different ILs.•More than 68% stability of cellulase in the presence of 50% w/w IL for 12 h.•Enzymatic saccharification of IL pretreated RS without water washing.