Screening of Cellulolytic Bacteria from Rotten Fruits and Optimization of Cellulase Production by Paenibacillus dendritiformis PQ845045 using the Response Surface Methodology

Bacterial cellulase production remains limited by suboptimal culture conditions, resulting in high production costs and restricting its industrial applications. This research aimed to determine γ-haemolytic degrading bacteria cellulose and to optimize cellulase production. Of 42 strains isolated on a reconstituted medium supplemented with carboxymethylcellulose used as the exclusive carbon source, only 19 showed significant cellulose hydrolysis capacity. Following morphological and metabolic characteristics analyses, together with haemolysis tests, 16S rRNA gene sequencing identified four promising strains belonging to three bacterial species: Paenibacillus dendritiformis (PQ845045) and Bacillus altitudinis (PQ845085 and PQ845089), all γ-haemolytic, as well as Mammaliicoccus lentus (PQ845126), a β-haemolytic strain. Cellulase production by Paenibacillus dendritiformis was optimized using a single-factor approach and a central composite experimental design. The results showed optimal activity at pH 7, with this activity increasing as the concentrations of the various carbon and nitrogen compounds increased. The statistical model, which was generally significant, allowed for a maximum activity of 3.32 IU/mL, representing an approximately 6-fold increase compared to the non-optimized medium. This activity was obtained in a medium containing 25 g/L of carboxymethylcellulose, 3 g/L of yeast extract, and 2.5 g/L of NaCl at 32.5 °C. Response surface analysis identified temperature as the main factor significantly influencing cellulase production. These results highlight the cellulolytic potential of P. dendritiformis B17C and position this strain as a promising candidate for the biotechnological production of cellulase.