Pilot-scale processing of Miscanthus x giganteus for recovery of anthocyanins integrated with production of microbial lipids and lignin-rich residue

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-04, Vol.485, p.150117, Article 150117
• Main Authors: Banerjee, Shivali, Dien, Bruce S., Eilts, Kristen K., Sacks, Erik J., Singh, Vijay
• Format: Article
• Language: English
• Subjects: 09 BIOMASS FUELS; Anthocyanins; Biorefinery; Lignin; Microbial Lipids; Miscanthus x giganteus; Pilot-scale
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2024.150117

[Display omitted] •Zero-waste MxG biorefinery was demonstrated at a commercially relevant scale.•Pilot-scale pretreatment of MxG recovered >70 % w/w of anthocyanins as co-products.•Enzymatic hydrolysis of pretreated biomass produced 238 g/L of total sugar.•The MxG sugars were utilized to produce microbial lipids with titers of 10–11 g/L.•Post-enzymatic hydrolysis residue was enriched in lignin 1.7-fold. Chemical-free hydrothermal pretreatment of Miscanthus x giganteus (Mxg) at the lab scale using high liquid-to-solid ratios resulted in the recovery of anthocyanins and enhanced enzymatic digestibility of residual biomass. In this study, the process is scaled up by using a continuous hydrothermal pretreatment reactor operated at a low liquid-to-solid ratio (50 % w/w solids) as an important step towards commercialization. Anthocyanin yield was 70 % w/w at the pilot scale (50 kg of Mxg), compared to the 94 % w/w yield achieved at the lab scale (0.5 g of Mxg). The pretreated biomass was subsequently refined mechanically using a disc mill to increase the accessibility of cellulose by cellulases. Enzymatic saccharification of the pretreated and disc-milled residue yielded 238 g/L sugar concentration by operating in fed-batch mode at 50 % w/v solids content. Two strains of Rhodosporidium toruloides were evaluated for converting the hydrolysate sugars into microbial lipids, and strain Y-6987 had the highest lipid titer (11.0 g/L). Further, the residue left after enzymatic saccharification was determined to be enriched 1.7-fold in the lignin content. This lignin-rich residue has value as a feedstock for the production of sustainable aviation fuel precursors and other high-value lignin-based chemicals. Hence the proposed biorefinery based on Mxg creates an opportunity for generating revenue from multiple high-value products. As the demand for biofuels and biobased products is rising, the biorefinery products from Mxg would create a niche in the industrial sector.