We isolated thirty thermophilic fungi with ability to grow at 45 °C on medium containing wheat bran and casein as carbon sources and produced proteases in both SSF and SmF (data not shown). The fungus strain F.2.1.4 presented the highest protease activity and was sub-jected to taxonomic characterization.
Analyses of macro and micro-morphological characteristics accommodated the isolate F.2.1.4 in the genus Myceliophthora due to the presence of spreading colonies with dense aerial mycelium and blastic conidia often borne in ampulliform swellings (Van Oorschot, 1980). Particularly, this isolate produced pulverulent pale mycelium, obovoid conida measuring 5.65-7.91 x 3.39-4.52 μm as well as conidia walls finely ornamented. Based on such char-acters the isolate F.2.1.4 is similar to Myceliophthora thermophila, however, some slight morphological differences were observed, for instance, M. thermophila has pale brown, woolly colonies and a variable range of conidia sizes 4.5-11 x 3.0-4.5 µm (Van Oorschot, 1977).
Data derived from BLAST (ITS-rDNA region) showed that the isolate F.2.1.4 had high sequence similarities (99-96%) with three unidentified Myceliophthora spp. isolated from geothermal soils in China; and 95-94% of sequence similarities with different strains of the Ascomycota genus Corynascus (one of the Myceliophthora teleomorphic states), includ-ing three new species: C. verrucosus sp. nov., C. similis sp. nov., C. sepedonium, C. sexualis sp. nov. (Stchigel et al., 2000). The phylogenetic tree showed that the isolate F.2.1.4 clustered with the three Myceliophthora strains from China (Figure 1).
Molecular and phylogenetic results corroborate the data from morphological analyses and considering the combined methods used for fungus identification, the thermophilic isolate F.2.1.4 was identified as Myceliophthora sp.. Species on this genus are commonly found in soil, molding open-stack alfalfa ensilage, fir and spruce pulpwood chips and wheat straw compost (Van Oorschot, 1980). Moreover, results derived from conventional, molecular and phylogenetic analyses suggest that isolate F.2.1.4 likely represent a new species in the genus Myceliophthora. Additional taxonomic analyses will be performed in order to confirm the new species hypothesis.
Enzyme production in solid-state (SSF) and in submerged (SmF) fermentations
Figure 2 shows the profile of protease production by Myceliophthora sp. in SSF and SmF. The maximum enzyme production was obtained in the third fermentation day in SSF (1.78 U mL-1) and in the forth day in SmF (0.38 U mL-1). The higher protease production achieved in SSF corroborate data reported by several investigators and reinforce the hypothesis that production of extracellular enzymes is higher in SSF since the conditions of this fermentation system are similar to natural fungal growth media (Aguilar et al., 2004; Silva et al., 2007; Morita et al., 1999; Ramesh and Lonsane, 1991). The data also showed that wheat bran, that...