# Green Production and Biotechnological Applications of Cell Wall Lytic Enzymes
## 5 Bio-Applications of CWLEs
### Use of Plant-Expressed CWLEs in Medical and Nutraceutical Fields and in Food Processing  
Expression of CWLEs in crop plants and microalgae has two major advantages: the low production costs and their GRAS (Generally Recognized As Safe) designation, which allows exploitation of such CWLEs for the production of nutraceuticals and bio-active compounds for human use; however, this does not mean that plant-expressed CWLEs are totally safe for human health. Importantly, CWLEs may be expressed in a glycosylated form, as in the case of the recombinant proteins targeted to the extracellular environment, causing allergic reactions in humans. In order to circumvent the possibility of such an undesired effect, recombinant CWLEs with future uses in humans can be expressed in the chloroplast or targeted to the cytoplasm where glycosylation events do not occur. Amongst the many applications of CWLEs, biomedicine and nutraceuticals are two emerging fields where plant-expressed CWLEs find many applications. In general, the most employed CWLEs in this field are fungal cellulases and \(\beta\)-glucosidaseases. Cellulases from _Trichoderma reesei_ are included in enzymatic blends that favor the digestion of cellulose-rich fibrous substances, such as fruits and vegetables, cereals, legumes, bran, nuts, seeds, and soy, in order to help people suffering from slow digestion and particular metabolic disorders. Moreover, cellulases may be used in combination with chitinases and lysozyme to constitute a mixture capable of degrading chitin (i.e., a long-chain polymer of N-acetylglucosamine mainly found in crustacean and insect exoskeleton) into chitosan (i.e., a \(\beta\)-1,4-linked polysaccharide constituted by p-glucosamine and N-acetyl-p-glucosamine) [143]. Chitosan and its derivatives find applications as components in surgical sutures, bone rebuilding, hemostatic dressing, and skin reconstruction. Moreover, chitosan is used in combination with metals as anticoagulants, antibacterials, and anticancer and antidiabetic agents [144; 145]. Chitosan is also the main component of many nutraceuticals because of its capability of acting as an immune-stimulatingfactor in the human immune system [146; 147]. The broad substrate specificity of several \(\beta\)-glucosidase can be exploited for converting plant metabolites into biologically active compounds. It is the case of flavanone glycosides from citrus extracts that are converted into flavanone aglycones by the \(\beta\)-glucosidase from _Pyrococcus furiosus_[148]. Upon hydrolysis, flavanone glycosides such as naringin, narirutin, naringenin and hesperidin are converted into aglycones, with strong anticancer activities, by a single-step reaction [149]. Importantly, these metabolites can be obtained by agricultural scraps such as grapefruit and orange-peel extracts, indicating that the achievement of high-value molecules from waste materials is feasible. Moreover, CWLEs can promote the release of many molecules with antioxidant and coloring properties (i.e., carotenoids) from raw plant materials that, in turn, are used as natural food colorants. \(\beta\)-glucosidase find applications also in food processing since most of them are characterized by lactase activity (i.e., capability of degrading lactose in glucose and galactose), pointing to their exploitation in the processing of dairy products for lactose-intolerant people. CWLEs are a powerful resource for food biotechnology because of their applicability in a broad range of processes. Fruit and vegetable juice clarification, viscosity reduction of nectars, modification of organoleptic properties, carotenoid extraction, olive oil extraction, and quality improvement of bakery products are the processes in which CWLEs are commonly exploited. The cloudiness of fruit and vegetable juices is a result of floating polysaccharide materials such as cellulose, hemicellulose, lignin, pectin, and starch. The presence of these materials in juice negatively affects the quality of the product and lowers user demand.