Production of Biomass-Degrading Enzymes by Trichoderma reesei Using Liquid Hot Water-Pretreated Corncob in Different Conditions of Oxygen Transfer

Abstract

Enzymatic hydrolysis accounts for 20% of the total cost in the conversion process of lignocellulosic biomass into bioethanol. Therefore, production of biomass-degrading enzymes by using lignocellulosic residue as a fermentation substrate may be an alternative to decrease the production costs. In this study, corncob (CC) has been pretreated by liquid hot water (LHW) at 200°C for 30 min and used as inducer source for production of biomass-degrading enzymes by Trichoderma reesei MUM 97.53. The pretreatment was used to increase the cellulose content and the accessibility to lignocellulosic material. Although the filamentous fungus secreted a broad range of cellulolytic and hemicellulolytic enzymes when grown on untreated CC, higher enzyme productions were obtained when cultured on LHW-pretreated CC in a 2-L stirred tank bioreactor (STB). Besides, the effects of aeration (2 and 4 vvm) and agitation (150 and 250 rpm) rates on enzyme production were studied by submerged fermentation in a batch STB and correlated with the volumetric oxygen transfer coefficient (k L a). Maximal cellulase, xylanase, and βxylosidase productions were found at 150 rpm and 4 vvm, while the highest β-glucosidase levels were obtained at 150 rpm and 2 vvm, that corresponded to k L a values of 32.50 h −1 and 16.41 h −1 , respectively. At higher agitation, a lower enzymatic production was observed probably due to the high shear stress in the fungal hyphae.

Xylanase production by Trichoderma virens MLT2J2 under solid-state fermentation using corn cob as a substrate

“…Trichoderma virens MLT2J2 showed reduced relative activity of xylanase below 50% for pH 7.0-8.0. This result is in agreement with previous studies that the most fungal xylanase activities are optimum at moderately acidic to alkaline pH range; for instance, pH 3-4 for T. asperellum UC1 (Ezeilo et al 2019), pH 5,0 for T. harzianum (Ahmed et al 2012), pH 5.3 for T. asperellum USM SD4 xylanase (Ajijolakewu et al 2016), pH 6.0 for T. reesei MUM 97.53 (Michelin et al 2019), and pH 9-10 for Sarocladium kiliense (Tarayre et al 2015).…”

“…being among the prolific producers of xylanases, the high enzyme production cost and poor stability are major deterrents in widening their applications in the manufacturing industry. To date, xylanases producing Trichoderma species which include Trichoderma harzianum (Pathak et al 2014;Lopez-Ramirez et al 2018), T. viride (Soliman et al 2021, Ja'afaru 2013Ishida et al 2020), T. reesei (Michelin et al 2019;Hirasawa et al 2018), T. asperellum UC1 (Ezeilo et al 2019;Dortavásquez et al 2019), T. virens (Tarayre et al 2015;El-Shishtawy et al 2015;Ngikoh et al 2017), and T. pleuroticola (Korkmaz et al 2017) have been studied. Inoculation of T. virens can degrade cellulose and hemicellulose in biomass (empty fruit bunches and palm oil mill effluent) hence speed up the composting process.…”

“…The fungal enzymes are greatly influenced by the nature, physical factors, and chemical composition of the carbon source (Peciulyte et al 2014). The different kinds of 6531 sources and chemical composition of biomass have an apparent influence on the secreted enzymes activities in cultures of fungal (Alvira et al 2013) and previous studies reported several works on using corn cob (Soliman et al 2012;Michelin et al 2019), wheat bran and rice bran (Pathak et al 2014;El-Shishtawy et al 2015), sugarcane bagasse (Mahamud and Gomes 2012), oil palm empty fruit bunch and leaves (Ajijolakewu et al 2016;Ngikoh et al 2017;Ezeilo et al 2019) as substrates for fermentation processes to produce hemicellulases. In this study, we used corn cob due to its high hemicellulose content and rich carbon, and also nitrogen sources for the growth and stimulation natural habitat of microorganisms (Elegbede and Lateef 2018).…”

Catalytic conversion of corncob biomass into bioethanol

“…Various pretreatment techniques have been evolved since the last decades to expose more cellulose to access for hydrolysis 2 . Generally, the pretreatment methods are classified into a physical method—liquid hot water, 3 ultrasound, 4,5 and microwave irradiation 6,7 ; chemical method—acid hydrolysis, 8 alkaline, 9 and oganosolv 10 ; physiochemical method—ozonolysis 11 wet oxidation 12 ; and biological method—trichoderma, 13 white‐rot fungi, 14 serpulalacrymans brown rot fungi, and cellulase enzymatic hydrolysis or their combination 15 . Ultrasound pretreatment has the benefit of lesser use of chemicals, limitation of equipment corrosion, and reduced processing time.…”

Ideal Feedstock and Fermentation Process Improvements for the Production of Lignocellulolytic Enzymes

“…The physical pretreatment methods such as hot water and steam are employed at different temperature and time conditions. For example, Michelin et al [107] employed the liquid hot water treatment method at different time periods and reported maximum production of hydrolytic enzymes after a 30-min treatment. On the other hand, the steam pretreatment method can give better results at shorter periods [89].…”