Bioprocessing of shrimp wastes to obtain chitosan and its antimicrobial potential in the context of ethanolic fermentation against bacterial contamination.

This study investigated the bioprocessing of shrimp wastes to obtain chitin and its deacetylated product chitosan by a fermentation process mediated by Lactobacillus plantarum. The concentrations of glucose, bacterial inoculum, and shrimp wastes in the Man, Rogosa and Sharpe medium were optimized for the fermentation process performed in shake flasks to achieve the maximum titratable acidity to obtain chitin. The experiments were scaled up in a 700-mL working volume bioreactor, and the resulting chitin was deacetylated by the autoclave method. The bioextracted chitosan was characterized (Fourier transform infrared spectroscopy [FTIR], deacetylation degree, and molecular weight) and evaluated for its antimicrobial effects by comparing it with a commercial chitosan sample in the context of the ethanolic fermentation process for fuel alcohol production. The effect of chitosan on such a fermentation process has not been determined yet. The bacterial contaminant Lactobacillus fermentum and the main agent of ethanolic fermentation Saccharomyces cerevisiae were cultured in semi-synthetic medium and co-cultured in sugarcane juice to verify the effect of chitosan on their growth. The bioextracted chitosan (molecular weight 4.0 × 105 g mol-1 and deacetylation degree 80%) was comparable to commercial chitosan, although higher concentrations of the former were required to achieve similar antimicrobial activities. Both commercial and bioextracted chitosan samples exhibited antimicrobial activity against S. cerevisiae and L. fermentum, but the concentration that caused the inhibition of yeast growth was almost tenfold higher than for the bacterium. Moreover, bioextracted chitosan showed no yeast inhibition or lethality in the range of 0.0075-0.96% while for the bacterium, growth inhibition occurred in concentrations varying from 0.24 to 0.48% and lethality of more than 99% at 0.96%. These results indicate the potential use of chitosan and especially of bioextracted chitosan in the bioethanol industry as a safer and more natural approach to combat unwanted bacterial contamination.

Sugarcane vinasse and microalgal biomass in the production of pectin particles as an alternative soil fertilizer.

High methoxyl pectin was used as biopolymeric matrix to produce a novel slow release soil fertilizer added with sugarcane vinasse and lipid extracted microalgal (Desmodesmus subspicatus) biomass residue (LMBR). Vinasse acted as the biopolymer solvent, providing greater stability to pectin gel, and as a source of nitrogen (N), potassium (K), calcium (Ca) and magnesium (Mg). LMBR (0.5%) was considered a complementary source of N and micronutrients, copper (Cu), iron (Fe) and zinc (Zn). Compared to blank pectin particles, the particles with vinasse and LMBR showed homogeneous polymer matrix, spherical shapes, higher soluble matter release and enhanced mechanical properties. Scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analysis indicated the incorporation of microalgal biomass and nutrients from vinasse. Higher rates of biodegradation as well as larger degree of mineralization were found over a period of 36 days for vinasse and LMBR particles. These particles exhibit good perspectives as an alternative fertilizer for agriculture applications and represent an innovative solution for vinasse and LMBR final disposal.