Produção e propriedades antimicrobianas de hidrogéis formulados com lignina extraída do bagaço de caju

Abstract

The cashew industry is a sector focused on the production of resources, mainly derived from the cashew tree. Brazil, particularly the Northeast region, is one of the world's largest producers of cashew, with states such as Ceará, Piauí, Rio Grande do Norte, and Bahia leading the production. A significant problem for the sector currently is the expansion of agricultural areas, which has negative impacts on soil biodiversity. Another aggravating factor is the low added value of by-products, such as cashew nut shells and cashew apple bagasse, which are underutilized or only used as supplements for animal feed or for energy generation through burning. However, several studies have been conducted to explore possible applications of these by-products. Some of these studies focus on the use of cellulose and hemicellulose present in cashew apple bagasse for the production of xylitol and ethanol. Other studies investigate the potential of cashew nut shells in biodiesel production, as well as the use of cashew tree leaves in the production of films with antioxidant and antimicrobial properties. However, lignin, which constitutes the largest fraction of cashew apple bagasse (33% m/m), still faces difficulties in its application in the market. Although it is widely available and easily extracted, lignin is often considered a negative factor in industrial processes, such as biofuel production. In this context, the focus of this work is to evaluate the use of cashew apple bagasse lignin in biomedical applications, especially in the dermatological field, by verifying the material's potential as an antimicrobial agent, which would make it a highly competitive material in the market. Then, in this work, lignin was extracted from cashew apple bagasse, and its antimicrobial and hygroscopic properties were evaluated for the synthesis of biomedical materials, such as dressings. The hydrogel formed with 3% (w/v) of lignin showed high swelling with liquid retention above 920% and was effective against the growth of Escherichia coli and Staphylococcus aureus. In addition, bandages using a layer of polyester and hydrogellignin were developed and they showed hydroscopic properties and antimicrobial activity against E. coli and S. aureus bacteria. The formulated materials did not show cytotoxic effects on Artemia salina micro crustaceans. Then, this work resulted in obtaining a material with added cashew apple bagasse lignin, a promoter of antimicrobial activity against E. coli and S. aureus, having low or no cytotoxic effect against eukaryotic cells of A. salina and with potential use in biomedical applications.