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Fungal hydrophobins have potential for several applications because of their abilities to change the hydrophobicity of different surfaces. Yet because of their tendency for aggregation and attachment to interfacial areas only few production processes have so far been reported. Towards the development of a heterologous production system, we report here the expression of a class I hydrophobin DewA of Aspergillus nidulans in Hypocrea jecorina (Trichoderma reesei). Using the H. jecorina hfb2 (class II hydrophobin-encoding) promoter and lactose as a carbon source, only a minor fraction of the DewA remained cell-wall-bound and the majority of it secreted into the medium with up to 15% of the total secreted protein. N-terminal amino acid sequencing showed that it was correctly processed. In contrast, no DewA was produced under the cel7A (cellobiohydrolase I) promoter, although its mRNA was abundantly detected in the cells. This lack of secretion is not due to trapping in the cell wall or to its degradation because of the unfolded protein response. Recombinant DewA could be conveniently precipitated from the culture filtrate, and its bioactivity proven by its ability to stably bind to hydrophilic and hydrophobic surfaces (glass and Teflon, respectively). We thus consider H. jecorina as a promising host for further optimization of DewA production.

Fungi of the genus Trichoderma are soilborne, green-spored ascomycetes that can be found all over the world. They have been studied with respect to various characteristics and applications and are known as successful colonizers of their habitats, efficiently fighting their competitors. Once established, they launch their potent degradative machinery for decomposition of the often heterogeneous substrate at hand. Therefore, distribution and phylogeny, defense mechanisms, beneficial as well as deleterious interaction with hosts, enzyme production and secretion, sexual development, and response to environmental conditions such as nutrients and light have been studied in great detail with many species of this genus, thus rendering Trichoderma one of the best studied fungi with the genome of three species currently available. Efficient biocontrol strains of the genus are being developed as promising biological fungicides, and their weaponry for this function also includes secondary metabolites with potential applications as novel antibiotics. The cellulases produced by Trichoderma reesei, the biotechnological workhorse of the genus, are important industrial products, especially with respect to production of second generation biofuels from cellulosic waste. Genetic engineering not only led to significant improvements in industrial processes but also to intriguing insights into the biology of these fungi and is now complemented by the availability of a sexual cycle in T. reesei/Hypocrea jecorina, which significantly facilitates both industrial and basic research. This review aims to give a broad overview on the qualities and versatility of the best studied Trichoderma species and to highlight intriguing findings as well as promising applications.

Light represents a major carrier of information in nature. The molecular machineries translating its electromagnetic energy (photons) into the chemical language of cells transmit vital signals for adjustment of virtually every living organism to its habitat. Fungi react to illumination in various ways, and we found that they initiate considerable adaptations in their metabolic pathways upon growth in light or after perception of a light pulse. Alterations in response to light have predominantly been observed in carotenoid metabolism, polysaccharide and carbohydrate metabolism, fatty acid metabolism, nucleotide and nucleoside metabolism, and in regulation of production of secondary metabolites. Transcription of genes is initiated within minutes, abundance and activity of metabolic enzymes are adjusted, and subsequently, levels of metabolites are altered to cope with the harmful effects of light or to prepare for reproduction, which is dependent on light in many cases. This review aims to give an overview on metabolic pathways impacted by light and to illustrate the physiological significance of light for fungi. We provide a basis for assessment whether a given metabolic pathway might be subject to regulation by light and how these properties can be exploited for improvement of biotechnological processes.