Avaliação da utilização de resíduo agroindustrial oriundo da produção de biodiesel de semente de tabaco para a obtenção de polihidroxialcanoatos (PHA).

Abstract

Waste in general can be considered one of the most serious problems faced today, with damages that go beyond the environmental sphere. Current production methods increasingly seek alternatives that can minimize the generation of waste, or technologies that allow the return of waste to the production chain. In this context, one of the alternatives that has been investigated is the substitution of conventional plastics for biopolymers. Biopolymers are biologically based and use renewable and sustainable sources of raw material, including waste from other agro-industrial processes. The objective of this work was the use of a residue from the production of biodiesel as a low cost substrate for obtaining the biopolymer Polyhydroxybutyrate (PHA). The residue, tobacco seed cake, underwent a pre-treatment stage, consisting of an acid hydrolysis with 5% Sulfuric Acid (v / v), neutralization with Potassium Hydroxide up to pH = 7, being incorporated in a culture medium . The bacterium used was characterized by isolation, characterization and molecular identification. Assays of PHA accumulation were performed with different inoculum time conditions, media formulation and culture strategy, in order to optimize the polymer obtaining. Glucose was used in the control experiments to compare PHA accumulation. Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR) were used to analyze the presence and structure of the polymer. The substrate used was analyzed by High Performance Liquid Chromatography (HPLC) and centesimal analysis. The analyzed residue presented composition (%) of 4.51 ± 0.56 for ashes, 31.94 ± 4.87 for proteins, 27.05 ± 5.30 for lipids and 36.48 ± 9.04 for carbohydrates, in Centesimal analysis. The hydrolyzed obtained from the pretreatment showed glucose, arabinose and xylose in its composition. The presence of lipid residue in the hydrolyzed, which was used by the bacteria in the assays, was verified. The isolated bacteria, called E10, was identified as a Bacillus pumilus strain, with satisfactory growth in the culture medium used. The best cultivation condition, evidenced by the accumulation of PHA inside the cells, was defined at 28ºC, grown in an orbital incubator at 150 revolutions per minute, for a time of 40 hours. Polymer formation occurred in the cultures, which was extracted, purified and analyzed. The data obtained from the analysis of the polymer point to a copolymer formed by Polyhydroxybutyrate-co-hydroxyvalerate (P (3-HB-co-HV).) Glucose cultures (positive control) formed only P (3-HB). The methodology used and the interpretation of the data of the cultivation experiments, it is believed that the tobacco seed cake hydrolyzate has potential of applicability to obtain PHA B. pumilus E10 bacterium proved to be a good accumulator of PHA. In the future the analysis of the lipid and protein composition of the hydrolyzate, the test with strains of other standard bacteria, the kinetics of the accumulation of PHA and the quantification of the polymer production.