Bacteria, yeast, and microalgae are sources of biomolecules such as enzymes, lipids, pigments, organic acids and, proteins for industrial application. These high-added-value biomolecules are often intracellularly bioaccumulated, and their recovery involves several downstream processes, in which the most crucial stage is the disruption of the cell wall. The choice of the method influences the further downstream steps and, consequently, its complexity and cost. In this review, severe and gentle methods currently used for disruption or permeabilization of bacteria, yeast, and microalgae were discussed based on their principle, application, and feasibility. Also, recent studies regarding the microbial cell disruption were presented in order to facilitate the choice of the more effective method. Some factors such as cell wall composition, nature of biomolecule, purity degree, scalability, and energy input are necessary to be considered on selecting the most appropriate disruption method. The severe methods, such as high pressure-homogenization, and ultrasonication present higher yield, lower cost, and feasibility to scale-up when compared to the gentle methods. However, in order to achieve a higher recovery yield, further studies must focus on the optimization of operational parameters and on the combination of severe and gentle methods.

In this study, two green synthesis routes were used for the synthesis of Ag/ZnO nanoparticles, using cassava starch as a simple and low-cost effective fuel and Aloe vera as a reducing and stabilizing agent. The Ag/ZnO nanoparticles were characterized and used for bacterial disinfection of lake water contaminated with Escherichia coli (E. coli). Characterization indicated the formation of a face-centered cubic structure of metallic silver nanoparticles with no insertion of Ag into the ZnO hexagonal wurtzite structure. Physicochemical and bacteriological analyses described in “Standard Methods for the Examination of Water and Wastewater” were used to evaluate the efficiency of the treatment. In comparison to pure ZnO, the synthesized Ag/ZnO nanoparticles showed high efficiencies against Escherichia coli (E. coli) and general coliforms present in the lake water. These pathogens were absent after treatment using Ag/ZnO nanoparticles. The results indicate that Ag/ZnO nanoparticles synthesized via green chemistry are a promising candidate for the treatment of wastewaters contaminated by bacteria, due to their facile preparation, low-cost synthesis, and disinfection efficiency.

Optimization of lactic fermentation for extraction of chitin from freshwater shrimp waste

This study aimed to extract the oil from macauba pulp using a low-pressure solvent extraction, as well as characterisation of the extracts and defatted meal obtained using different solvents (n-hexane, ethyl acetate and isopropanol). Results reported higher yields in oil, 27.43%, using isopropanol (P0.05) on the composition; however, in the quantification of free glycerol compounds, isopropanol showed higher levels, 104.15mg 100g-1, of these compounds (P<0.05). Meals had higher ash, protein and fibre content when compared to pulp. Thus, oil removal can be stated to promote water retention capacity; however, it has no influence on the other technological characteristics evaluated.