Heliyon (Sep 2024)
Production of cellulases by Xylaria sp. and Nemania sp. using lignocellulose substrates for bioethanol production from maize cobs
Abstract
Two species of Xylaria (KM01, KM03) and Nemania sp.KM02 isolated from decaying plant biomass were evaluated for their ability to produce cellulases on maize cob, eucalyptus, and cypress substrates under solid-state fermentation. A total of 10 fungal samples from decaying plant biomass were collected from Karura forest based on morphological variations. The fungi isolated were screened for cellulase activity and positive isolates were selected for the study. ITS4 R and ITS86 F primers were used to identify the fungal isolates with accuracy ranging from 98 % to 100 %. The crude cellulases produced was assayed for FPase, exoglucanase, endoglucanase and β-glucosidase. Cellulases of Xylaria sp. KM01 produced higher FPase and exoglucanase (2.01 ± 0.13 IU/ml and 0.94 ± 0.08 IU/ml) on pretreated maize cobs with 0.1M HCl at 121oC, while that of Xylaria sp.KM03 produced higher β-glucosidase and endoglucanase (588.6 ± 64.2 IU/ml and 3.59 ± 0.02 IU/ml) on maize cobs pretreated with 0.1M NaOH at 121oC. However, cellulases of Xylaria sp. KM01 produced higher β-glucosidase and FPase (629.7 ± 20.2 IU/ml and 1.67 ± 0.03 IU/ml) on untreated maize cobs after the 9th day of incubation, whereas cellulases of Xylaria sp.KM03 and Nemania sp.KM02 produced higher endoglucanase and exoglucanase (2.80 ± 0.21 IU/ml and 0.83 ± 0.02 IU/ml) on untreated maize cobs after the 3rd and 6th day of incubation. Saccharification of maize cobs by cellulase of Xylaria sp.KM03 produced the highest reducing sugars at 8 % substrate loading (10.17 ± 0.37 mg/ml) after 72 h of incubation. Simultaneous hydrolysis and fermentation of maize cobs by cellulase of Nemania sp.KM02 and Saccharomyces cerevisiae yielded higher bioethanol (28.72 ± 3.82 mg/ml) after 96 h of fermentation. Maize cob is established as a suitable feedstock for cellulases and bioethanol production.
