Title: Waste-to-value: Microbial engineering and fermentation optimization for sustainable and cost-effective bioplastic and biochemical production from agro-industrial waste
Abstract:
Waste-derived biomass streams offer a promising resource for the cost-effective production of high value-added bioproducts in a circular bioeconomy. As part of the CBE project PROMOFER, this work outlines a comprehensive strategy to convert agro-industrial and lignocellulosic wastes—such as wastewater, low-value starches, whey permeate, and agricultural residues—into polyhydroxybutyrate-co-valerate (PHBV), a biodegradable bioplastic, and 2,3-butanediol (2,3-BDO), a platform chemical for biobased polyurethane.
The process begins with the transformation of waste into volatile fatty acids (VFAs) and sugar-rich hydrolysates through acidogenic fermentation and enzymatic pretreatment. These feedstocks are then utilized by microbial strains (Cupriavidus necator, Bacillus megaterium, Bacillus spp.), which have been enhanced through random mutagenesis and metabolic engineering. Key modifications include removal of energy-wasting pathways and upregulation of biosynthetic enzymes to improve PHBV accumulation and 2,3-BDO production.
In addition to improving biosynthetic performance, a central objective of this strategy is to increase microbial tolerance to common fermentation inhibitors. These include VFAs—such as acetic, propionic, and butyric acid—as well as toxic by-products from biomass pretreatment, including furfural, hydroxymethylfurfural (HMF), and phenolic compounds. Enhanced resistance to these compounds leads to greater process stability and higher fermentation yields.
Fermentation processes are scaled and optimized to meet the specific needs of target applications. PHBV is produced in fed-batch systems under controlled conditions to meet performance requirements for packaging and agricultural uses. 2,3-BDO production is optimized through statistical design of media and digital process modeling, enabling large-scale manufacturing for bio-based synthetic leather. These improvements are crucial to reducing overall production costs and enhancing the commercial viability of biobased alternatives.
Environmentally friendly downstream processing completes the value chain. PHBV is extracted using green solvents and enzymatic methods, while 2,3-BDO is recovered through membrane-based and aqueous two-phase extraction systems designed for minimal environmental impact.
This waste-to-value approach developed in PROMOFER provides a scalable, economically competitive, and sustainable platform for the industrial production of bioplastics and biochemicals, replacing fossil-based counterparts in key sectors.
