Cellulolytic potential of bacteria isolated from Australian marsupial herbivores

Abstract

Cellulose, the most abundant renewable biopolymer on Earth, represents a key resource for biofuel production but requires efficient enzymatic hydrolysis to overcome its structural resistance. In this study, cellulose-degrading bacteria were isolated from fecal samples of two Australian marsupial herbivores: the koala (Phascolarctos cinereus) and the common wombat (Vombatus ursinus). Ten bacterial isolates were screened for cellulolytic activity; four strains exhibited substantial hydrolysis zones on carboxymethyl cellulose (CMC) agar and demonstrated elevated activity in fermentation broth. 16 S rRNA gene sequencing identified three isolates as Streptomyces spp. (K1, KFK6, KFWH) and one as Enterobacter sp. (KFWI). Optimization of cellulase production was conducted by varying incubation periods (24–168 h), pH (3.5–8.5), temperatures (27–50 °C), additives (NaCl, CaCl₂, ZnSO₄, MgSO₄, SDS, EDTA, Tween 80, Triton X-100), carbon sources (glucose, fructose, lactose, sucrose, CMC), and nitrogen sources (yeast extract, ammonium chloride, peptone, urea). K1, KFK6 and KFWI showed maximum CMCase production at 37 °C, whereas KFWH showed maximum production at 40 °C. The optimal pH was 7.5 for K1 and KFWI, and 6.5 for KFK6 and KFWH. Maximum enzyme production occurred at 72 h for K1 and KFWI, 120 h for KFK6, and 96 h for KFWH. These marsupial-derived isolates represent promising candidates for future studies on lignocellulosic biomass hydrolysis and other biotechnological applications.