Produção, caracterização e aplicação de nanocelulose do bagaço de caju

Abstract

Nanocellulose material has gained great prominence in the economic and industrial sector due it exhibits excellent properties such as high mechanical strength, high surface and biodegradability. However, there is still a need to explore new materials and more efficient methods for preparing nanocellulose. In this context, this objective of this work is obtained nanocellulose, via acid and enzymatic hydrolysis routes, both sequential with the ultrasonic process, using pretreated cashew apple bagasse (CAB), and to evaluate its application in the production of biofilms. Initially, CAB was pretreated using alkaline pretreatment (NaOH), analyzing different percentages of CAB, 5 % and 10 % w/v (denominated CAB-PTA-5 and CAB-PTA-10). Also, it was evaluated the pretreatment performed with acid followed by alkali using H2SO4 and NaOH, and 20 % w/v of initial load CAB, being the pretreated CAB named CAB-PTA-HA. Subsequently, it was evaluated the obtaining of nanocellulose by acid hydrolysis (methods II and III) and enzymatic hydrolysis (methods IV and V), varying the sulfuric acid concentration, enzyme loading, and time. The material obtained by these methods was characterized by Fourier transform infrared spectrophotometry (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and thermogravimetric analysis (TGA). The CAB-PT-HA had a higher cellulose content when compared to CAB pretreated only with alkali (CAB-PTA-5 and CAB-PTA-10), which in turn showed a greater amount of residual lignin. CAB-PT-HA showed greater thermal stability. The results confirmed the obtaining of nanocellulose by acid hydrolysis conducted according to methods II (BC-PTA-HA) and III (BC-PTA-10), which presented the shape of rods with a diameter ranging from 30 nm to 100 nm, with BC-PTA-5 (method III) nanospheres with diameters from 100 nm to 120 nm were obtained. Furthermore, the nanostructures obtained from CAB-PTA-10 and CAB-PTA-5 contained residual lignin. By the enzymatic hydrolysis process, using BC-PT-HA with a load of 7.5 FPU/g cellulose and 24 h of hydrolysis it was possible to obtain nanospheres with diameters from 57.26 nm to 220.66 nm, and the resulting liquid fraction contained 1.51 g/L of glucose, with a yield of 175,6 mg of glucose per g of BC-PT-HA, presenting itself as a possible source of carbon to obtain products of industrial interest. The material resulting from enzymatic hydrolysis (method IV) was used in the production of biofilms, which have potential for applications in the food packing material. Therefore, from BC it was possible to obtain nanocellulose, resulting in another application for this residue.