Cellulases production on paper and sawdust using native Trichoderma asperellum

Univ. Sci. 23 (3): 419-436, 2018. doi: 10.11144/Javeriana.SC23-3.cpop Bogotá original article Cellulases production on paper and sawdust using native Trichoderma asperellum Y-Maritza Zapata1, Angelica Galviz-Quezada1, Víctor-Manuel Osorio-Echeverri2, * Edited by Juan Carlos Salcedo-Reyes () 1. Semillero de investigación sifacs, Facultad de Ciencias de la Salud, Institución Universitaria Colegio Mayor de Antioquia, Carrera 78 # 65-46, Medellín, Colombia. 2. Grupo Biociencias, Facultad de Ciencias de la Salud, Institución Universitaria Colegio Mayor de Antioquia, Carrera 78 # 65-46, Medellín, Colombia. * Received: 26-07-2017 Accepted: 27-09-2018 Published on line: 02-11-2018 Citation: Zapata YM, Galviz-Quezada A, Osorio-Echeverri VM. Cellulases production on paper and sawdust using native Trichoderma asperellum, Universitas Scientiarum, 23 (3): 419-436, 2018. doi: 10.11144/Javeriana.SC23-3.cpop Funding: Research Incubator Program of the Health Sciences Faculty (sifacs). Electronic supplementary material: N.A. Abstract Microbial cellulases are industrially used enzymes that catalyze the cleavage of the glycosidic bonds of cellulose. This hydrolysis yields sugars that can be used in processes such as bioethanol production. These enzymes are mainly produced by fungi belonging to the genus Trichoderma via submerged or solid state fermentation with cellulosic materials as substrates. Recent publications have increasingly demonstrated that alternatives to T. reesei enzymes in the production of second-generation biofuels exist. Here, cellulolytic activities of crude extracts obtained from a native isolate of T. asperellum from coffe pulp and a strain of T. reesei were evaluated. Solid state fermentations were performed using paper and sawdust as substrates. The activities were measured after 12 days of incubation. The extracts obtained from T. reesei showed higher cellulase and endoglucanase activities (6.5 and 5.8 U/g) than those obtained using T. asperellum (5.6 and 4.1 U/g) with paper as substrate. There were no significant differences between isolates when grown on sawdust. It was possible to verify that native T. asperellum was able to produce cellulases on lignocellulosic material such as moistened paper and sawdust without having undergone a chemical pretreatment. Keywords: cellulases; cellulolytic extracts; solid state fermentation; Trichoderma. Introduction Cellulose is an important structural component of the plant cell wall and therefore, one of the most abundant biological materials on Earth. It is a polysaccharide consisting of a linear chain of several hundreds to many thousands of β (1→4) linked D-glucose units [1]. Cellulose, hemicellulose, and lignin are the main components of the lignocellulosic biomass, such as seed husks, bagasse, woodchips, straw, dry leaves, and sawdust. This lignocellulosic biomass represents an economical, plentiful, renewable energy source because it is generally waste material [2, 3]. Universitas Scientiarum, Journal of the Faculty of Sciences, Pontificia Universidad Javeriana, is licensed under the Creative Commons Attribution 4.0 International Public License 420 Cellulases production using Trichoderma asperellum These waste materials can be used to produce biofuels, the use of which can help reduce carbon dioxide emission as well as dependence on fossil fuels. For this process, polymers in the lignocellulosic biomass must be broken down into fermentable sugars. The enzymatic hydrolysis of these compounds is an environment-friendly process catalyzed by both types of cellulases (endo-1,4-b-D-glucanase, EC 3.2.1.4; exo-b-1,4-glucan cellobiohydrolase, EC 3.2.1.91; and b-glucosidase, EC 3.2.1.21) and hemicellulases (exo-1,4-b-xylosidase, EC 3.2.1.37 and endo-1,4-b-xylanase, EC 3.2.1.8) [4, 5]. Also, this hydrolysis can be performed under neutral pH and low temperature and with low by-product formation, thus being highly efficient [6]. Nevertheless, high concentrations of enzymes are required to scale-up cellulose hydrolysis to industrial levels. Therefore, the study of biotechnology-based approaches is important for their use in production of cellulase-producing microorganisms, which are of interest also in the textile, paper, pharmaceutical, food, and detergent industries [6, 7]. This study focussed on Trichoderma, one of the most studied cellulaseproducing genera of fungi [4]. T. reesei is the most studied species for cellulolytic enzyme production at an industrial level. It is a common soil fungus found in the rhizospheres of crop plants, decaying wood, and other decomposing materials. It is characterized by rapid growth, mostly bright green conidia, and a repetitively branched conidiophore structure [8]. Although it is believed that T. reesei is the only and indispensable choice for enzymatic cellulose saccharification and mutant strains with high cellulolytic activity, such as T. reesei Rut C30 have been developed, recent publications have increasingly demonstrated that fungi other than T. reesei are used for cellulolytic enzymes production and it is necessary to optimize the culture conditions for these fungi as well as the technology required for efficient cellulase production in bioreactors [9-12]. Several strains of Trichoderma have been used in submerged fermentations to study cellulase production using substrates, such as cellulose [5], pulp mill lime mud [13], flower stems [14, 15], and crop residues [16]. Likewise, researchers have also used corncob [6], mushroom compost [17], oat straw [18], wheat bran [18, 19], rice husk and bran [20], rice straw [19, 21], cauliflower and legumes residues [21], and sugarcane bagasse [19, 22] as substrates in solid state fermentations (SSF). Additionally, enzymatic hydrolysis of corn stover, rice straw, sawdust, and paper has been performed with cellulases produced by Trichoderma to obtain fermentable sugars [2, 5, 6, 23]. However, these substrates must undergo pretreatment for lignin removal, because lignin constitutes a barrier to cellulose breakdown by microorganisms [6, 24]. Universitas Scientiarum Vol. 23 (3): 419-4366 http://ciencias.javeriana.edu.co/investigacion/universitas-scientiarum 421 Zapata et al. Waste paper can be used as a substrate in SSF to produce cellulases with fungi of the genus Trichoderma [3]. This type of fermentation, in comparison to others, enables the use of low-cost substrates, recovery of enzymes with higher concentrations, and faster growth of aerobic microorganisms, such as the filamentous fungi. SSF also uses less energy and has lower sterility requirements than those of submerged fermentations [25]. Paper has low lignin and high cellulose contents and does not require any chemical pretreatment for its use in cellulase production. Hence, besides being environment-friendly, waste paper is an ideal substrate for fungal cellulase production. The objective of this work was to evaluate cellulolytic enzyme production in SSF with a native isolate (...truncated)