Sustainability approaches for agrowaste solution: Biodegradable packaging and microbial polysaccharides bio-production.

Global growth impacts on the increased use and demand for natural resources, requiring solutions for the high volume of industrial waste and by-products generated from the most diverse commercial areas, mainly the food sector. Among the main residues with a large volume generated, those from fruit processing, grain cleaning in processing units, vegetables, and discards from the animal production industry stood out. Approximately 1.3 billion all food produced worldwide is lost or wasted per year being fruits, vegetables, roots, and tubers responsible for about half of the total amount. Many of these by-products have interesting nutrients in their composition such as fibers, proteins, and bioactive compounds. An interesting example is the sugarcane bagasse. Fibrous residue, derived from sugarcane extraction, the bagasse represents about 30-34 % of the total sugarcane mass. This is one of the most abundant cellulosic residues and contains approximately 39 % of cellulose, 28 % of hemicellulose, and 18 % of lignin. Therefore, as well as the bagasse, several residues from agroindustrial can be considered promising alternative substrates, being valuable sources for the development of high-value-added products, such as biopolymers, bioenergy, and chemical products. In addition, the reuse of agroindustrial wastes may be considered an attractive option for reducing the environmental impact caused by their generation. In the case of biopolymers, the energy savings of bio-based polymers is around 20-50 GJ/t of polymer. In this review, we have selected two commercially promising approaches to the application and use of agroindustrial residues, aiming their use for biodegradable packaging and microbial polysaccharides bio-production, improving overall sustainability and economic aspects of the scientific research, technology and modern industry.

Chitosan/carboxymethylcellulose polyelectrolyte complexes (PECs) are an effective material for dye and heavy metal adsorption from water.

Granular macroscopic chitosan/carboxymethylcellulose polyelectrolytic complexes (CHS/CMC macro-PECs) were produced and tested as adsorbents for six pollutants often present in wastewaters: sunset yellow (YS), methylene blue (MB), Congo red (CR) and safranin (S), cadmium (Cd2+) and lead (Pb2+). The optimum adsorption pH values at 25 °C were 3.0, 11.0, 2.0, 9.0, 10.0, and 9.0 for YS, MB, CR, S, Cd2+, and Pb2+, respectively. Kinetic studies indicated that the pseudos-econd order model best represented the adsorption kinetics of YS, MB, CR, and Cd2+, whereas the pseudo-first order model was the most suitable for S and Pb2+ adsorption. The Langmuir, Freundlich, and Redlich-Peterson isotherms were fitted to experimental adsorption data, with the Langmuir model providing the best fit. The maximum adsorption capacity (qmáx) of CHS/CMC macro-PECs for the removal of YS, MB, CR, S, Cd2+, and Pb2+ was 37.81, 36.44, 70.86, 72.50, 75.43, and 74.42 mg/g, respectively (corresponding to 98.91 %, 94.71 %, 85.73 %, 94.66 %, 98.46 %, and 97.14 %). Desorption assays showed that CHS/CMC macro-PECs can be regenerated after adsorbing any of the six pollutants studied, with possibility of reuse. These results provide an accurate quantitative characterization of the adsorption of organic and inorganic pollutants on CHS/CMC macro-PECs, indicating a novel technological applicability of these two inexpensive, easy-to-obtain polysaccharides for water decontamination.