Distribution of a novel enzyme of sialidase family among native filamentous fungi.

Sialidases (neuraminidases, EC 3.2.1.18) are widely distributed in biological systems but there are only scarce data on its production by filamentous fungi. The aim of this study was to obtain information about sialidase distribution in filamentous fungi from non-clinical isolates, to determine availability of sialidase gene, and to select a perspective producer. A total of 113 fungal strains belonging to Ascomycota and Zygomycota compassing 21 genera and 51 species were screened. Among them, 77 strains (11 orders, 14 families and 16 genera) were able to synthesize sialidase. Present data showed a habitat-dependent variation of sialidase activity between species and within species, depending on location. Sialidase gene was identified in sialidase-positive and sialidase-negative strains. . Among three perspective strains, the best producer was chosen based on their sialidase production depending on type of cultivation, medium composition, and growth temperature. The selected P. griseofulvum Р29 was cultivated in 3L bioreactor at 20 °C on medium supplemented with 0.5% milk whey. The results demonstrated better growth and 2.3-fold higher maximum enzyme activity compared to the shaken flask cultures. Moreover, the early occurring maximum (48 h) is an important prerequisite for future up scaling of the process.

Potential of ligninolytic enzymatic complex produced by white-rot fungi from genus Trametes isolated from Bulgarian forest soil.

Because of the crucial role of ligninolytic enzymes in a variety of industrial processes, the demand for a new effective producer has been constantly increasing. Furthermore, information on enzyme synthesis by autochthonous fungal strains is very seldom found. Two fungal strains producing ligninolytic enzymes were isolated from Bulgarian forest soil. They were identified as being Trametes trogii and T. hirsuta. These two strains were assessed for their enzyme activities, laccase (Lac), lignin peroxidase (LiP) and Mn-dependent peroxidase (MnP) in culture filtrate depending on the temperature and the type of nutrient medium. T. trogii was selected as the better producer of ligninolytic enzymes. The production process was further improved by optimizing a number of parameters such as incubation time, type of cultivation, volume ratio of medium/air, inoculum size and the addition of inducers. The maximum activities of enzymes synthesized by T. trogii was detected as 11100 U/L for Lac, 2.5 U/L for LiP and 4.5 U/L for MnP after 14 days of incubation at 25°C under static conditions, volume ratio of medium/air 1:6, and 3 plugs as inoculum. Among the supplements tested, 5% glycerol increased Lac activity to a significant extent. The addition of 1% veratryl alcohol had a positive effect on MnP.

Cold-stress response during the stationary-growth phase of Antarctic and temperate-climate Penicillium strains.

Cold-induced oxidative stress during the aging of three Penicillium strains (two Antarctic and one from a temperate region) in stationary culture was documented and demonstrated a significant increase in the protein carbonyl content, the accumulation of glycogen and trehalose, and an increase in the activities of antioxidant enzymes (superoxide dismutase and catalase). The cell response to a temperature downshift depends on the degree of stress and the temperature characteristics of the strains. Our data give further support for the role of oxidative stress in the aging of fungi in stationary cultures. Comparing the present results for the stationary growth phase with our previous results for the exponential growth phase was informative concerning the relationship between the cold-stress response and age-related changes in the tested strains. Unlike the young cells, stationary-phase cultures demonstrated a more pronounced level of oxidative damage, as well as decreased antioxidant defence.

Production, purification, and characterization of a novel cold-active superoxide dismutase from the Antarctic strain Aspergillus glaucus 363.

The Antarctic fungal strain Aspergillus glaucus 363 produces cold-active (CA) Cu/Zn-superoxide dismutase (SOD). The strain contains at least one gene encoding Cu/Zn-SOD that exhibited high homology with the corresponding gene of other Aspergillus species. To our knowledge, this is the first nucleotide sequence of a CA Cu/Zn-SOD gene in fungi. An effective laboratory technology for A. glaucus SOD production in 3 L bioreactors was developed on the basis of transient cold-shock treatment. The temperature downshift to 10 °C caused 1.4-fold increase of specific SOD activity compared to unstressed culture. Maximum enzyme productivity was 64 × 10(3) U kg(-1) h(-1). Two SOD isoenzymes (Cu/Zn-SODI and Cu/Zn-SODII) were purified to electrophoretic homogeneity. The specific activity of the major isoenzyme, Cu/Zn-SODII, after Q-Sepharose chromatography was 4000 U mg(-1). The molecular mass of SODI (38 159 Da) and of SODII (15 835 Da) was determined by electrospray quadropole time-of-flight (ESI-Q-TOF) mass spectrometry and dynamic light scattering (DLS). The presence of Cu and Zn were confirmed by inductively coupled plasma mass spectrometry (ICP-MS). The N-terminal amino acid sequence of Cu/Zn-SODII revealed a high degree of structural homology with Cu/Zn-SOD from other fungi, including Aspergillus species.