Exo- and endoglucanase production by Curvularia affinis using bean (Phaseolus vulgaris L.) waste biomass

Background In many countries, agricultural residues are generated in large quantities, and most of these are underutilized and considered waste, especially in developing countries. Result In this study, Curvularia affinis was isolated from the leaves of Phaseolus vulgaris L. beans and identified using 18S rRNA sequencing. C. affinis was tested for exo- and endoglucanase production using biomass of bean waste compared with the use of microcrystalline cellulose (MCC) and carboxymethylcellulose (CMC) as its growth substrates. C. affinis was better able to produce exo- and endoglucanase enzymes on bean waste biomass than on MCC and CMC. The highest activities of exo- and endoglucanase were detected with substrate concentrations 2% using MCC or CMC and with 4% using bean waste. The optimum incubation period for enzymes activity was 6 days with MCC or CMC (activity was 5.90 and 2.99 U/g of exoglucanase and endoglucanase, respectively) and 8 days with bean waste where activity was 3.64 U/g and 0.92 U/g of exoglucanase and endoglucanase, respectively. Exo- and endoglucanase production showed the highest activity at pH 5-6. In process wherein surfactant (Tween 80) was used, the exoglucanase activity gradually increased from 5.92 U/g to 6.20 U/g and then decreased to 5.70 U/g at 0.50% compared with that using the MCC substrate. The exoglucanase activity gradually increased from 3.80 U/g at 0.0% to 4.12 U/g at 0.20% and then decreased to 3.01 U/g at 0.50% Tween 80 using bean waste. Pretreated bean biomass also yielded higher enzyme production than the non-pretreated biomass. Alkaline-pretreated biomass showed the highest enzyme production compared with acid-treated residues, followed by the H2O2-treated ones. Conclusion The study concluded that C. affinis produce exo- and endoglucanase enzymes using cheap and abundant biomass of beans. Moreover, optimization of enzymes indicated that pretreatment of biomass bean biomass is a good choice process for enhanced enzymes productivity.