Xylanase-assisted bioconversion and bioelectricity production in microbial fuel cells: A novel strategy for renewable energy generation

The isolation of stable and efficient enzymes from microbial sources plays a crucial role in mitigating the capital intensiveness of lignocellulosic biomass bioconversion. In this study, a cellulase-free xylanase enzyme was identified and characterized from a bacterial isolate. The xylanase demonstrated high specificity for the degradation of xylan, an abundant component of plant biomass, without the interference of cellulase activity. The enzyme exhibited optimum activity at 50 ℃ and pH 7. Additionally, it demonstrated thermal stability within the temperature range of 35–65 ℃ and pH stability across pH values of 4–10. Metal ions such as Zn^2 + and Mg²⁺ enhanced while, Ca²⁺, K²⁺, Co²⁺, Cu²⁺, Hg²⁺, Fe²⁺, and Na²⁺ ions declined the enzyme activity. The specific activity of xylanase was 430 IU/mg of protein. The xylanase enzyme demonstrated absolute substrate specificity by being active on beechwood xylan and only slightly active on birchwood, larchwood, and wheat arabinoxylan (soluble and insoluble), but inactive on avicel, carboxymethylcellulose, and starch. The kinetic parameters of the enzyme were also significant. Further, the xylanase-treated substrate at various concentrations, was once again utilized in microbial fuel cells (MFC) to produce bioelectricity. Co-culturing of Bacillus sp. with Pseudomonas aeruginosa generated a maximum of 12.08 W/m³ power density from the MFC study. Around 82 % of chemical oxygen demand (COD) removal was achieved after the spent media treatment. The energy recovery was 18 % approximately. These findings highlight the enzyme's potential for industrial applications and its role in renewable bioenergy production through MFCs, demonstrating a promising integration of waste biomass utilization with clean energy generation.