Optimization of microfibrillated cellulose isolation from cocoa pod husk via mild oxalic acid hydrolysis: A response surface methodology approach.

Theobroma cacao L. species, cultivated worldwide for its valuable beans, generates up to 72% weight of the fruit as waste. The lack of reutilization technologies in the cocoa agroindustry has hindered the exploitation of valuable bio-components applicable to the generation of high value added bioproducts. One such bioproduct is microfibrillated cellulose (MFC), a biopolymer that stands out for its desirable mechanical properties and biocompatibility in biomedical, packing, 3D printing, and construction applications. In this study, we isolated microfibrillated cellulose (MFC) from cocoa pod husk (CPH) via oxalic acid hydrolysis combined with a steam explosion. MFC isolation started with the Solid/Liquid extraction via Soxhlet, followed by mild citric acid hydrolysis, diluted alkaline hydrolysis, and bleaching pre-treatments. A Response Surface Methodology (RSM) was used to optimize the hydrolysis reaction at levels between 110 and 125 °C, 30-90 min at 5-10% (w/v) oxalic acid concentration. The cellulose-rich fraction was characterized by Fourier-Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) analyses. Characterization analyses revealed a cellulose-rich polymer with fibers ranging from 6 to 10 µm, a maximum thermal degradation temperature of 350 °C, and a crystallinity index of 63.4% (peak height method) and 29.0% (amorphous subtraction method). The optimized hydrolysis conditions were 125 °C, 30 min, at 5% w/v oxalic acid: with a 75.7% yield. These results compare with MFC obtained through highly concentrated inorganic acid hydrolysis from different biomass sources. Thus, we show a reliable and greener alternative chemical treatment for the obtention of MFC.

Moringa oleifera Lam. leaf powder antioxidant activity and cytotoxicity in human primary fibroblasts.

Moringa oleifera Lam. (MO) leaf powder has been well studied, however, understanding how extraction methods of antioxidant compounds affect human primary fibroblasts still needs to be determined. The antioxidant capacity was analyzed through a copper reduction capacity method and primary human skin fibroblasts were evaluated for cytotoxicity using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Antioxidant activity under the influence of methanolic solvents (Trolox equivalents of 160.18 nmol/µL) was 17 times higher than under aqueous solvents. Interestingly, the aqueous extract showed less toxicity in comparison to the methanolic, as cells resulted more susceptible to concentrations ranging from 0.05 to 5 mg/L. Although, MO methanol solvent showed a higher antioxidant capacity in comparison to the aqueous solvent, it presented greater cytotoxicity. Thus, it is concluded that the aqueous extract could be suitable for downstream processing and applications.