Treatments with Natural Enzymes to Produce Cellulose and their Contribution to Synthesis of Nanocellulose (CNCs) from Rice Husk

Recent research has managed to produce Nanocellulose (CNCs) using biomass such as rice husk, although with low yields when employing the enzymatic synthesis route. Nanocellulose, an innovative material with applications in biotechnology, has revolutionized science and the environment by potentially replacing plastic and glass in the creation of new devices. The trial carried out yielded Cellulose, from previous treatments of rice hulls with natural enzymes (Bromelain and Papain). A cooking treatment was prepared with 5% NaOH, taking a ratio of 1:10 shell/solution. Subsequently, Bleaching solutions were compared: 1% hydrogen peroxide (H2O2) and 1% sodium hypochlorite (NaClO) solution. Additionally, it was also to the enzyme plus CaCl2 10%. Finally, a pre-treatment with hydrochloric acid (HCl) was used for both products at a concentration of 0.65% w/w. For nanocellulose synthesis, 1 mL of the stock solution of the following enzymes was added: D-(+)-cellobiose, cellobiohydrolase, endo-1,4-β-D-glucanase, and β-glucosidase. Two tests were carried out (Test 1) using all the enzymes together (exo and endoglucanases) on cellulose, applied at the same time. (Test 2) The enzymes applied in pairs, exo or endoglucanases, in two different phases or times. The characterization of cellulose and nanocellulose was performed by techniques including SEM, FTIR, and DSC. The results obtained showed that previous treatments of rice hulls with natural enzymes (Bromelain and Papain) decreased by half (5.26%) the Nitrogen (N) present in vegetable tissue, to denature the present proteins. Facilitating subsequent cooking and consequently a higher yield (44%), or even better when mixed with 10% CaCl2 (47%). Additionally, it was shown that hydrogen peroxide (H2O2) can be a substitute for (NaClO) for fiber whitening. The results were lower in both cases (1,1 and 1,06 %) than those obtained with other previously applied protocols to produce nanocellulose. Satisfactory results through characterization demonstrated the synthesis of nanocrystals in the 200 nm range, although better management is still needed to obtain higher yields.