# Cellulases Production by a _Trichoderma_ sp. Using Food Manufacturing Wastes
## 1 Introduction  
The production of food manufacturing wastes (FMWs) is potentially damaging to the environment; these materials, if not properly disposed of, can lead to the release of greenhouse gases or contaminate soil and water as they decay. Biotechnological approaches may be one solution to utilize these materials before they cause damage to the environment [1; 2]. In Chile, three important waste materials generated from the food manufacturing industry are olive-mill solid waste (OMSW), tomato pomace (TP), and grape pomace (GP). OMSW is a sub-product of olive oil production by two-phase centrifugation. It is composed of a liquid fraction also known as \"alpechin\" and a semisolid residue known as \"alperujo\". The chemical characterization of \"alperujo\" reveals a high moisture content, slightly acidic pH, and high content of organic matter, mainly consisting of lignin, hemicellulose, and cellulose. Furthermore, \"alperujo\" contains lipids and water-soluble polyphenols [3; 4]. TP is a sub-product of tomato processing which mainly consists of peels and seeds and is composed of lignocellulosic material, proteins, minerals, and lipids [5]. GP is a sub-product of grape processing, mainly composed of lignocellulosic residues, glucan, alcohol, phenols, and flavonoids [6]. One of the simplest strategies for disposal of these FMWs is biodegradation through enzymatic attack. FMWs are mainly composed of lignocellulosic, of which cellulose is the major component (20-50% _w/w_) [7]. In nature, a wide range of microorganisms can use cellulose as a carbon and energy source. To accomplish this, fungi and bacteria secrete extracellular enzymes able to degrade this complex polymer [8]. Cellulose is hydrolyzed by three different classes of enzymes: endo-\(\beta\)-1,4-D-glucanases (EC 3.2.1.4), which hydrolyze internal \(\beta\)-1,4-glucoside linkages, 1,4-\(\beta\)-D-glucan cellobiohydrolases (EC 3.2.1.91), which cleave off cellulose fragments from the cellulose chain ends, generating the cellobiose disaccharide and \(\beta\)-D-glucosidases (EC 3.2.1.21), which use cellobiose hydrolysis to generate glucose [9]. Celluases have been applied in many different industries, such as food, textiles, pulp, paper and wastewater treatment of residue effluents [10; 11]. However, one of the most significant current applications is in bioethanol production from lignocellulosic materials. Bioethanol is considered a fuel alternative for reducing the dependence on crude oil [7]. The majority of bioethanol produced globally is made from biomass containing starch (from corn) or sucrose (from molasses or cane juice) [12]. However, bioethanol can also be made from non-edible lignocellulosic biomass like wood or agricultural residues [13]. Generally, the production of bioethanol from lignocellulosic biomass requires several steps: pretreatment, enzymatic hydrolysis to monomers (also called saccharification), fermentation, distillation, and dehydration [14]. The pretreatment phase can be performed using several different processes, such as concentrated acid hydrolysis, dilute acid hydrolysis, alkali treatment, sodium sulfite treatment, and steam explosion, among others [15]. The objective of the pretreatment is to remove lignin and improve the access of the enzymes to the cell wall carbohydrates (mainly cellulose) to obtain fermentable sugars [16]. The next step is saccharification, in which cellulases, typically from _Trichoderma_ spp., are applied to produce fermentable monomer sugars from polysaccharides, primarily cellulose [14]. After saccharification, sugar monomers can be fermented to ethanol, typically with _Saccharomyces_ spp., resulting in concentrations of 40-50 g/L [17]. Almost all commercially available lignocellulosic enzymes needed for the hydrolysis step are produced by fermentation with the ascomycete _Trichoderma resei_[18]. However, the purchase of this enzymes can make up 20-40% of the operating costs in a lignocellulosic biomass-based biorefinery.