Conversion of Typha Latifolia (Cattails) to organic acids via acidogenic fermentation for use in reductive bioleaching of metals

Abstract

The sustainable production of organic acids from non-food lignocellulosic biomass is critical for advancing circular bioeconomy strategies and reducing reliance on chemically synthesized leaching agents. This study investigates acidogenic fermentation of untreated Typha latifolia, an abundant wetland biomass, to generate organic acids suitable for bioleaching. Rather than focusing on yield maximization, this work identifies key operational controls governing acidogenic performance. A full factorial design evaluated organic loading (2–6% w/v), oxygen availability (aerobic vs. anaerobic), biomass condition (fresh vs. dried), and manganese supplementation (0–50 ppm) across batch and continuous systems. Oxygen availability emerged as the dominant control variable (p < 0.05), consistently controlling solution acidification dynamics (pH drop and rate of decline), which served as a consistent operational indicator of acidogenesis. Anaerobic conditions enabled rapid pH reduction to 4.5–5.0 within 3–5 days, while fresh biomass significantly enhanced acid production due to the availability of fermentable sugars. Manganese supplementation influenced acidification rates through synergistic interactions with biomass condition but did not control final acid yield. High-performance liquid chromatography confirmed acetic acid as the primary product ( 262.75 mg/L), alongside lactic and formic acids, indicating mixed-acid fermentation pathways. Biomass-to-acid organic acid production reached approximately 50% under optimal conditions, demonstrating the feasibility of direct bioconversion. Semi-continuous operation simplified process control, with oxygen regulation sufficient to maintain stable acidogenic performance. These findings establish that process simplicity, specifically, untreated biomass and oxygen-controlled fermentation, can outweigh traditional yield-focused strategies at scale. The results provide a practical framework for integrating biomass valorization with hydrometallurgical processes, enabling the direct use of fermentation-derived organic acids as reagents in reductive bioleaching systems.