# Oil Press-Cakes and Meals Valorization through Circular Economy Approaches: A Review
## 5 Possible Ways to Capitalize the by-Products Obtained from the Oil Industry
### Substrate for Functional Ingredient Production
#### 5.2.1 Enzymes  
Various enzymes have an important role in industrial application. They can be produced by solid-state fermentation using oil cakes/ meals as substrate, because they are cheap materials (reduce the cost production) rich in nutrients, carbon and nitrogen and are compatible for fungalspecies. Some examples are tannase, inulinase, \(\alpha\)-amylase, glucoamylase, protease, phytase, mannase, lipase and L-glutaminase (Table 4). Their production depends on incubation time and pH, moisture and particle sizes of substrate. Large particles and too much content in water prevent the digestion of raw material and microbial respiration which leads to poor growth and enzyme production [148]. Proteases are a group of enzymes with a role in the protein hydrolysis. Bacterial and fungal species such as _Bacillus horikoshii_, _Bacillus clausi I52_, _Penicillium sp._, _Candida utilis_, _Bacillus sp. 1-312_, _Apergillus_ oryzae _(NCIM No.649, NRRL 1808)_, _Streptomyces termovani gers_ were used for protease production with soybean (overheated), coconut, olive, palm, sesame and rapeseed oilcakes/meals as substrates [81,148]. [PERSON] et al. [149] studied the ability of non-edible Mahua and Jastropha cake to act as substrates for _A Aspergillus niger_ and _Paecilomyces variotii_ growth and produce enzyme. The study concluded that despite the low protease activities, solid-state fermentation is suitable in antinutrient removal. Lipases are hydrolytic enzymes with numerous applications in the pharmaceutical and cosmetic industries and in dairy and bakery foods. [PERSON] et al. [147], [PERSON] et al. [50] optimized the production of lipase through SSF with _Pseudomonas aeruginosa_ and _Apergillus ibericus_. The highest production was obtained when the substrate used resulted by combining two oilcakes: linseed/ olive and sesame/ palm kernel. The obtained enzyme can be used in esterification (butyl decanoate formation using 5% biocatalyst) and hydrolysis reactions (increase production in shorth-chain triacylglycerols). Lipase extracted from _Rhizomucos pusillus_, _Rhizopus rhizopodiformis_ and _Pseudomonas sp. S1_ cultivated on olive oil cake, are suitable for oily waste water treatment and biodiesel production [150]. The enzyme could be extracted also from _Penicillium simplicissimum_, _Candida rugosa_, _Penicillium Chrysogenum_ S1, and _Candida utilis_ inoculated on soybean, coconut, sesame and olive oilcakes [81,147,151]. L-asparaginase is an enzyme that can be used as a drug, due to its therapeutic effect against leukemia. A content of 90.025 IU, 310 U/gds and 5.75 U/gds was obtained in solid SSF from _Apergillus wentii_ NCIM 941, _Apergillus niger_ C4 and _Serratia marcescens_, cultivated respectively on palm, sesame oil and coconut cake [63,152,153]. \(\alpha\)-amylase used in starch liquefaction was produced from _A Aspergillus oryzae_, _A Aspergillus terreus_ UF39 cultivated on two oilcakes: coconut and groundnut [79,147]. Phytase, and glucoamylase have been produced using bacterial and fungal species such as _Bacillus licheniformis_, _A Aspergillus ficuum_, and _Thermonucor indica-seudaticae_ respectively growing on sunflower, rape/canola, and cotton oilcakes as substrates in solid state fermentation [10]. Xylanase, xylosidase, acetyl-xylan esterase and cellulase were produced in a SSF process with rapeseed/canola oilcake as the substrate, on which microorganisms such as _Trichoderma reesei_ and _Streptomyces termovani gers_ were grown. Alternately, _Apergillus oryzae_ produced protease, phytase and phosphatase [10,89]. L-glutaminase and phytase were produced using sesame oilcake as substrate and microorganisms such as _Zygosaccharomyces rouxii_, _Mucor racemosus_ and _Rhizopus oryzae_[151]. Use of coconut oilcake as a nutrient source grew a bacterial strain of _Staphococcus_ sp. and fungal species such as _Apergillus ficuum_, _Mucor racemosus_, _Rhizopus oryzae_, _Rhizopus oligosporus_ and _Apergillus niger_ to produce inulase, phytase, and glucoamylase [22,82,147]. [PERSON], et al.