Nowadays various industrial and urban activities are resulting in discharging of enormous quantities of various pollutants and their accumulation in the environment. Considering that the presence of heavy metals in wastewater is a serious threat to the environment and human health and that conventional methods for their removal are not highly efficient, the current study mainly focuses to estimate cyanobacterial capability to accumulate different heavy metals from water and compare bioaccumulation and biosorption processes. Cyanobacteria Nostoc sp. was used and five heavy metals were selected for this experiment (Cd2+, Cu2+, Pb2+, Ni2+, Zn2+). Examined concentrations of HMs were 20, 80 and 200 mg/dm3 for the bioaccumulation study while for biosorption experiments 20 and 80 mg/dm3 of each HMs were used. Living cells of Nostoc sp. have the highest affinity for Pb2+ (98.15%) and Cu2+ (95.14%) removal from the solution by bioaccumulation. During the biosorption process, dried biomass of Nostoc sp., besides Pb2+ (92.27%) and Cu2+ (96.00%), shows a high affinity for Cd2+ (91.00%) removal. Living cyanobacterial cells of Nostoc sp. was capable to accumulate 82% of Zn, while dried biomass adsorbs 87% of Zn2+. The highest bioaccumulation of Ni2+ was only 38% while using the process of biosorption it was significantly higher (63.80%). These results could provide a preliminary study for further investigation in the direction of the development of immobilized biosorbents which could be used for industrial effluent treatment.
The influence of temperatures (18, 22 and 26°C), salt (60, 70 and 80 g/kg) and starter culture (0, 0.025 and 0.050 g/kg) on physico-chemical and microbiological changes during fermentation in cabbage heads were investigated. The experiment was set up in industrial conditions, samples were taken after 0, 5, 12, 27 and 62 days in order to determine the changes in color, texture, biogenic amines content, microbiological parameters, pH, aw, total sugar content, total acidity and salt content. Analysis of variance and Principal component analysis were applied to get a better overview of differences between samples and the similarities between different fermentation conditions. Significant color changes and softening of cabbage tissue did not occurred during the entire fermentation process. Cadaverine was not detected in samples containing starter culture, also the results were in range for maximum allowed putrescine and cadaverine doses for all cabbage samples. Total number of molds increased, contrary to number of yeasts on the last examined day in comparison with raw cabbage sample. Enterobacteriaceae were not detected after 5th fermentation day, while sharp increase of lactic acid bacteria number occurred until 12th day, and on the 12th fermentation day was in range of 7.82 to 9.84 log cfu/g. The fermentation process led to decrease in pH, aw and total sugar content, meanwhile total acidity 0.54%-0.89% and salt content 2.08%-3.19% in the cabbage heads increased, in comparison with raw sample where results for total acidity and salt content were 0.13% and 0.05%, respectively. Additionally, according Principal component analysis, temperature of fermentation had the greatest influence on the fermentation process, followed by the application of starter culture and then concentration of added salt.
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