Enhanced production and partial purification of thermostable cellulase from Acinetobacter ursingii strain-A1 using mineral salt medium supplemented with agro-industrial wastes

The increasing industrial demand for enzymes, particularly cellulases, has driven the search for novel, cost-effective and thermostable enzymes from thermophilic microorganisms. This study aimed to isolate and identify thermophilic cellulolytic bacteria from a cow rumen-waste dumpsite and evaluate the production, partial purification, and biochemical characteristics of cellulase produced by the most efficient isolate using synthetic and agro-industrial waste-supplemented media. Eight cellulolytic bacterial species were isolated from cow rumen-waste dumpsite at 55 °C, and screened for cellulolytic potential qualitatively and quantitatively via congo red staining and DNS assay, respectively. The most efficient strain, selected based on its high enzymatic index, was identified through phenotypic, biochemical, and 16 S rRNA gene sequencing. Cellulase production was evaluated under submerged fermentation using synthetic NaCMC medium and an agro-waste-supplemented medium containing sugarcane bagasse and Bambara nut waste. The enzyme was partially purified using ammonium sulfate precipitation, ion-exchange chromatography, and acetone precipitation and subsequently characterized for temperature and pH stability and sensitivity to metal ions and EDTA. The most efficient isolate was identified through phenotypic, biochemical, and 16 S rRNA gene sequencing as Acinetobacter ursingii strain-A1 . This finding expands the functional diversity of the genus, which is not commonly recognized for strong cellulase production. Cellulase production was remarkably higher in the agro-waste-supplemented medium than in the synthetic NaCMC medium, demonstrating the synergistic contribution of lignocellulosic carbon and organic nitrogen sources. Partial purification achieved a 12.40-fold purification, with a specific activity of 23.92 U/mg and a recovery yield of 48.10%. The partially purified enzyme retained over 50% of its activity at 70–80 °C, exhibited optimum activity at pH 7.0, and showed appreciable tolerance under alkaline conditions. However, enzyme activity was significantly inhibited by selected metal ions and EDTA. Acinetobacter ursingii strain–A1 represents a promising and previously underexplored source of cellulase. The enhanced enzyme production obtained with inexpensive agro-industrial wastes, combined with the enzyme’s moderate thermostability, neutral pH preference, and distinct response to metal ions, demonstrates its potential for cost-effective lignocellulosic biomass conversion and selected high-temperature bioprocessing applications.