Cellulolytic activities ofChaetomium globosum on different cellulosic substrates

Chaetomium and Chaetomium-like Species from European Indoor Environments Include Dichotomopilus finlandicus sp. nov

The genus Chaetomium is a frequently occurring fungal taxon world-wide. Chaetomium and Chaetomium-like species occur in indoor environments, where they can degrade cellulose-based building materials, thereby causing structural damage. Furthermore, several species of this genus may also cause adverse effects on human health. The aims of this research were to identify Chaetomium and Chaetomium-like strains isolated from indoor environments in Hungary and Finland, two geographically distant regions of Europe with drier and wetter continental climates, respectively, and to study their morphological and physiological properties, as well as their extracellular enzyme activities, thereby comparing the Chaetomium and Chaetomium-like species isolated from these two different regions of Europe and their properties. Chaetomium and Chaetomium-like strains were isolated from flats and offices in Hungary, as well as from schools, flats, and offices in Finland. Fragments of the translation elongation factor 1α (tef1α), the second largest subunit of RNA polymerase II (rpb2) and β-tubulin (tub2) genes, as well as the internal transcribed spacer (ITS) region of the ribosomal RNA gene cluster were sequenced, and phylogenetic analysis of the sequences performed. Morphological examinations were performed by stereomicroscopy and scanning electron microscopy. Thirty-one Chaetomium sp. strains (15 from Hungary and 16 from Finland) were examined during the study. The most abundant species was Ch. globosum in both countries. In Hungary, 13 strains were identified as Ch. globosum, 1 as Ch. cochliodes, and 1 as Ch. interruptum. In Finland, 10 strains were Ch. globosum, 2 strains were Ch. cochliodes, 2 were Ch. rectangulare, and 2 isolates (SZMC 26527, SZMC 26529) proved to be representatives of a yet undescribed phylogenetic species from the closely related genus Dichotomopilus, which we formally describe here as the new species Dichotomopilus finlandicus. Growth of the isolates was examined at different temperatures (4, 15, 20, 25, 30, 37, 35, 40, and 45 °C), while their extracellular enzyme production was determined spectrophotometrically.

Optimization of synergism of a recombinant auxiliary activity 9 from Chaetomium globosum with cellulase in cellulose hydrolysis

Auxiliary activity family 9 (AA9, formerly known as glycoside hydrolase family 61 or polysaccharide monooxygenase) is a group of fungal proteins that were recently found to have a significant synergism with cellulase in cellulose hydrolysis via the oxidative cleavage of glycosidic bonds of cellulose chains. In this study, we report the active expression of a recombinant fungal AA9 from Chaetomium globosum (CgAA9) in a bacterial host, Escherichia coli, and the optimization of its synergistic activity in cellulose hydrolysis by using cellulase. The recombinant CgAA9 (0.9 mg/g cellulose) exhibited 1.7-fold synergism in the hydrolysis of Avicel when incubated with 0.9 filter paper units of Celluclast 1.5 L/g cellulose. The first study of the active expression of AA9 using a bacterial host and its synergistic optimization could be useful for the industrial application of AA9 for the saccharification of lignocellulose.

Functional analysis of the degradation of cellulosic substrates by a Chaetomium globosum endophytic isolate

Most photosynthetically fixed carbon is contained in cell wall polymers present in plant biomasses, the largest organic carbon source in the biosphere. The degradation of these polymers for biotechnological purposes requires the combined action of several enzymes. To identify new activities, we examined which enzymes are activated by an endophytic strain of Chaetomium globosum to degrade cellulose-containing substrates. After biochemical analyses of the secretome of the fungus grown on cellulose or woody substrates, we took advantage of the available genomic data to identify potentially involved genes. After in silico identification of putative genes encoding either proteins able to bind to cellulose or glycohydrolases (GHs) of family 7, we investigated their transcript levels by reverse transcription-quantitative PCR (RT-qPCR). Our data suggest that eight genes compose the core of the cellulose-degrading system of C. globosum. Notably, the related enzymes belong structurally to the well-described GH families 5, 6, 7, 16, and 45, which are known to be the core of the cellulose degradation systems of several ascomycetes. The high expression levels of cellobiose dehydrogenase and two GH 61 enzymes suggest the involvement of this oxidoreductive synergic system in C. globosum. Transcript analysis along with relevant coding sequence (CDS) isolation and expression of recombinant proteins proved to be a key strategy for the determination of the features of two endoglucanases used by C. globosum for the first attack of crystalline cellulose. Finally, the possible involvement of transcriptional regulators described for other ascomycetes is discussed.

Use of Saccharum spontaneum (wild sugarcane) as biomaterial for cell immobilization and modulated ethanol production by thermotolerant Saccharomyces cerevisiae VS3

Saccharum spontaneum is a wasteland weed consists of 45.10+/-0.35% cellulose and 22.75+/-0.28% of hemicellulose on dry solid (DS) basis. Aqueous ammonia delignified S. spontaneum yielded total reducing sugars, 53.91+/-0.44 g/L (539.10+/-0.55 mg/g of substrate) with a hydrolytic efficiency of 77.85+/-0.45%. The enzymes required for hydrolysis were prepared from culture supernatants of Aspergillus oryzae MTCC 1846. A maximum of 0.85+/-0.07 IU/mL of filter paperase (FPase), 1.25+/-0.04 IU/mL of carboxy methyl cellulase (CMCase) and 55.56+/-0.52 IU/mL of xylanase activity was obtained after 7 days of incubation at 28+/-0.5 degrees C using delignified S. spontaneum as carbon source under submerged fermentation conditions. Enzymatic hydrolysate of S. spontaneum was then tested for ethanol production under batch and repeated batch production system using "in-situ" entrapped Saccharomyces cerevisiae VS3 cells in S. spontaneum stalks (1 cm x 1 cm) size. Immobilization was confirmed by the scanning electron microscopy (SEM). Batch fermentation of VS3 free cells and immobilized cells showed ethanol production, 19.45+/-0.55 g/L (yield, 0.410+/-0.010 g/g) and 21.66+/-0.62 g/L (yield, 0.434+/-0.021 g/g), respectively. Immobilized VS3 cells showed maximum ethanol production (22.85+/-0.44 g/L, yield, 0.45+/-0.04 g/g) up to 8th cycle during repeated batch fermentation followed by a gradual reduction in subsequent cycles of fermentation.