Abstract

Background:
The buffalo rumen microbiome is enriched in functional genes, notably those encoding betaglucosidase which participate in polysaccharide breakdown. However, the characterization of enzymes and the application of buffalo rumen in biomass fermentation remain underdeveloped.

Aim:
This study aimed to elucidate the enzymatic profile of buffalo rumen microbiota and assess the effect of heat of ammonia-based pretreatment combined with enzymatic hydrolysis isolated from buffalo ruminal fluid in rice straw to produce bioethanol.

Methods:
A factorial experiment was performed with heat (H) and enzyme (E) combinations. The treatment was as follows: (1) no heat and commercial enzyme (H0E1), (2) heat and commercial enzyme (H1E1), (3) no heat and buffalo rumen enzyme (H0E2), and (4) heat and buffalo rumen enzyme (H1E2) with three replications. The enzyme activity, glucose, and ethanol levels were measured.

Results:
Betaglucosidase enzyme was the highest activity (64.23±12.37 U/g) in buffalo rumen fluid. The activities of carboxymethyl cellulase, xylanase, and exoglucanase activity were 50.36±8.05, 17.44±5.95, and 0.20±0.03 U/g, respectively. The interaction treatments impacted (p< 0.01) the glucose production. H1E1 treatment had the highest glucose content (193.94±14.51 g/L) among all treatments. Moreover, the glucose level in the H0E1 group was higher than that in the H0E2 and H1E2 groups (102.96±27.59 vs 0.91±0.15 and 1.32±0.37 g/L, respectively). The combination treatments had no effect (p> 0.05) on ethanol production. Heat treatment did not (p> 0.05) influence the ethanol content. However, enzyme treatment affected (p< 0.01) the ethanol level. The ethanol production in the H0E1 and H1E1 groups (0.55±0.13 and 0.99±0.02% v/v) was higher than the ethanol content in the H0E2 and H1E2 treatments (0.19±0.11 and 0.28±0.10 % v/v).

Conclusion:
Buffalo rumen-derived cellulase can convert cellulose in rice straw into glucose. However, the glucose content in the buffalo rumen enzyme treatment was lower than that of the commercial enzyme.

Key words: Bioethanol; Biomass; Buffalo rumen microbiome.