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The fungal strain Aspergillus fumigatus 3 2 isolated from the tailings pond at the copper mine "Vlaykov vruh," Bulgaria, showed high tolerance to Cu 2þ and Zn 2þ . This study was designed to explore the relationship between Cu 2þ and Zn 2þ tolerance and cellular response to oxidative stress. The model strain was identified to species level by morphological and molecular methods. Fungal cultures were exposed to enhanced concentrations of metal ions. The effect of Cu 2þ and Zn 2þ was evaluated by the changes in fungal growth and morphology, the level of oxidative stress biomarkers, and the antioxidant activities of enzymes such as superoxide dismutase (SOD) and catalase (CAT). Two different cellular responses occurred: The concentrations of up to 500 mg/mL caused enhanced levels of oxidative stress biomarkers (glycogen and trehalose accumulation and oxidatively damaged protein content), as well as an increase in SOD and CAT activities. The treatment with concentrations from 500 to 2000 mg/mL led to enhanced glycogen consumption, accelerated proteolysis, and a decrease in SOD and CAT activities. The present results provide additional information about the participation of oxidative stress and antioxidant defense in enhanced tolerance of fungi isolated from metal-polluted soils. Probably, survival at extremely high concentrations also requires the participation of other defense mechanisms. Furthermore, the enhanced understanding of these processes will provide essential tools for efficient remediation practices.

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Cold-active catalase (CAT) elicits great interest because of its vast prospective at the medical, commercial, and biotechnological levels. The study paper reports the production of cold-active CAT by the strain Penicillium griseofulvum P29 isolated from Antarctic soil. Improved enzyme production was achieved by optimization of medium and culture conditions. Maximum CAT was demonstrated under low glucose content (2%), 10% inoculum size, temperature 20°C, and dissolved oxygen concentration (DO) 40%. An effective laboratory technology based on changing the oxidative stress level through an increase of DO in the bioreactor was developed. The used strategy resulted in a 1.7-and 1.4-fold enhanced total enzyme activity and maximum enzyme productivity. The enzyme was purified and characterized. P. griseofulvum P29 CAT was most active at approximately 20°C and pH 6.0. Its thermostability was in the range between 5°C and 40°C.

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The serious energy and environmental problems associated with the use of fossil fuels necessitate the search for alternative energy sources. One of the modern approaches is the anaerobic degradation of organic waste from agricultural wastes. The hydrogen and methane thus obtained are sources of environmentally friendly energy, which reduces carbon dioxide emissions from fossil fuels, as well as gaseous emissions resulting from natural degradation processes in the disposal of waste materials. The described two-stage anaerobic digestion (TPAD) system with an immobilized microbial consortium represents an innovative biotechnological approach that seeks to obtain an increased energy yield and raised degree of processing of waste materials. Some additional raw materials which represent waste materials from other industrial scale processes can be successfully applied and support higher biohydrogen production from wheat straw. The temperature regime suitable for wheat straw biodegradation is 55°C resulting in 2.5 time more biohydrogen production. The VFAs obtained from BR-1 are suitable substrate for the immobilized microbial consortia which is formed for nearly twenty days of bioreactor maintenance.