Key parameters optimization of chitosan production from Aspergillus terreus using apple waste extract as sole carbon source.

Chitosan is commonly obtained from shrimp and crab shell chitin by deacetylation; however, such supplies appear limitation. An alternative source of chitosan is cell wall in certain fungi. In this study, chitosan production through submerged fermentation of Aspergillus terreus on apple waste extract as sole carbon source was investigated. Monod equation with a maximum specific growth rate of 0.083 h-1 and half-saturation constant of 6.67 w/v% was best described the kinetic of growth. Results of response surface methodology showed the highest chitosan to substrate yield of 49.32 mg gsubstrate-1, chitosan to fungal biomass yield of 140.9 mg gcell-1, and fungal biomass to substrate yield of 0.387 gcell gsubstrate-1 were simultaneously obtained at temperature 30.0 °C, initial pH 5.98, and ammonium nitrate concentration 5.0 g L-1. The chitosan produced at the optimum condition was characterized by FTIR, TGA, and DSC analysis, and degree of deacetylation was 88.2%.

Biohydrometallurgy as an environmentally friendly approach in metals recovery from electrical waste: A review.

Nowadays, large amount of municipal solid waste is because of electrical scraps (i.e. waste electrical and electronic equipment) that contain large quantities of electrical conductive metals like copper and gold. Recovery of these metals decreases the environmental effects of waste electrical and electronic equipment (also called E-waste) disposal, and as a result, the extracted metals can be used for future industrial purposes. Several studies reported in this review, demonstrated that the biohydrometallurgical processes were successful in efficient extraction of metals from electrical and electronic wastes. The main advantages of biohydrometallurgy are lower operation cost, less energy input, skilled labour, and also less environmental effect in comparison with pyro-metallurgical and hydrometallurgical processes. This study concentrated on fundamentals and technical aspects of biohydrometallurgy. Some points of drawbacks and research directions to develop the process in the future are highlighted in brief.