Utilização de resíduos láticos poluentes nos substratos para produção de nanocelulose bacteriana

Abstract

The production of NCB (bacterial nanocellulose) depends mainly on the availability of the nutritional components of the production medium. Different carbon sources and cultivation media have been reported for NCB production, however, Hestrin-Schramm (HS) medium remains the most commonly used. Its high production cost, due to components such as yeast extract and peptone, still represents a major challenge in meeting commercial manufacturing requirements. In this work, a modified culture medium was developed in order to produce bacterial nanocellulose membranes (NCB), lowering their production cost and reusing polluting waste. A bibliographical survey was carried out on NCB, the main bacteria that produce biofilm and the nutrients used in conventional culture media. In this context, dairy waste is a good option for developing a modified medium, as it has high concentrations of carbon and nitrogen, as well as other nutrients. The dairy industry is one of the main industries in the country, and stands out worldwide for its cheese production. However, two important wastes are generated from this production: whey (SL) and filtering water (AF). Both are extremely polluting effluents and need to be treated before being disposed of. For the production of NCB, a control condition was used with HS medium (GC) and six conditions were carried out for the media modified for each waste (SL and AF), with Condition A - Pure waste; Condition B: HS + 20% waste; Condition C: HS + 50% waste; Condition D: HS without peptone replaced by waste. Condition E: HS without yeast extract replaced by the residue; and Condition F: HS without peptone and yeast extract replaced by the residue. To carry out the experiments, the pH of these effluents was altered to between 4.5 and 4.7. The average wet weight showed that using SL in condition D resulted in an NCB membrane weighing more than the control group (CG), while the same condition using AF was not superior to the CG, but was very close. Scanning electron microscopy (SEM) analysis shows that the microfibrils are arranged differently depending on the condition and residue used. Fourier Transform Infrared Spectroscopy (FTIR) analysis shows a pattern in the curvatures of the graph, where all the conditions worked on are similar to the GC. The results obtained indicate that the bacterium Komagataebacter xylinus produced NCB in modified medium with pH adjustments under the proposed conditions. In this way, both SL and AF can be used in culture media to produce NCB in a sustainable way, especially AF, which, according to a literature survey, has few records of reuse.