Fatty Acid Composition in Ergosteryl Esters and Triglycerides from the Fungus Ganoderma lucidum

Quantitative Proteomic Profiling of Fungal Growth, Development, and Ochratoxin A Production in Aspergillus ochraceus on High- and Low-NaCl Cultures

Dry-cured meat products are worldwide food with high-salt content, and filamentous fungi are beneficial to the maturation process. However, some salt-tolerant strains of Aspergillus and Penicillium produce ochratoxin A (OTA) on these products and thus threaten food safety. In our study, proteomic analysis was performed to reveal the mechanism of adaptability to high-salt environment by Aspergillus ochraceus. Twenty g/L and 70 g/L NaCl substrates were used to provide medium- and high-NaCl content environments, respectively. The NaCl addition could induce fungal growth, but only 20 g/L NaCl addition could induce spore production while 70 g/L repressed it. Proteomics analysis identified 2646 proteins in A. ochraceus fc-1, of which 237 and 251 were differentially expressed with 20 g/L and 70 g/L NaCl addition, respectively. Potential factors affecting fungal growth and development were identified by GO and KEGG analyses of biological process, cellular component, and molecular function terms. The results revealed that ergosterol synthesis pathway was significantly upregulated with 20 g/L and 70 g/L NaCl addition. However, fungal growth and development including OTA production were complex processes associated with many factors including nutrient uptake, cell membrane integrity, cell cycle, energy metabolism, intracellular redox homeostasis, protein synthesis and processing, autophagy, and secondary metabolism. Reactive oxygen species may be an important window to understand the mechanism that medium-salt content was conducive to intracellular signal transduction while high-salt content caused oxidative stress. The findings would help to improve the processes and storage conditions of dry-cured meat products.

Co-production of microbial oil and exopolysaccharide by the oleaginous yeastSporidiobolus pararoseusgrown in fed-batch culture

The production cost of microbial oil was reduced by improving the exopolysaccharide (EPS) production to share the production cost using Sporidiobolus pararoseus JD-2. Batch fermentation demonstrated that S. pararoseus JD-2 has the potential to co-produce oil and EPS with 120 g L⁻¹ glucose, 20 g L⁻¹ corn steep liquor and 10 g L⁻¹ yeast extract as carbon and nitrogen sources. Using fed-batch fermentation for 72 h resulted in oil and EPS production of 41.6 ± 2.5 g L⁻¹ and 13.1 ± 0.6 g L⁻¹ with the productivity of 0.58 g L⁻¹ h⁻¹ and 0.182 g L⁻¹ h⁻¹, respectively. The fat soluble nutrients in the oil were studied, indicating that it was constituted of 79.19% unsaturated fatty acids and contained 505 mg per kg-oil of carotenoids. Moreover, the EPS contained only one type of polysaccharide; the main monosaccharide compositions were galactose, glucose and mannose in a proportion of 16 : 8 : 1. These results implied that EPS produced by S. pararoseus JD-2 was a new type of EPS.

The production cost of microbial oil was reduced by improving the exopolysaccharide (EPS) production to share the production cost using Sporidiobolus pararoseus JD-2.

Fungus-larva relation in the formation of Cordyceps sinensis as revealed by stable carbon isotope analysis

For more than one thousand years, Cordyceps sinensis has been revered as a unique halidom in the Qinghai-Tibetan Plateau for its mysterious life history and predominant medicinal values. This mysterious fungus-larva symbiote also attracted the over-exploitation, while several problems on the initial colonization of Ophiocordyceps sinensis in the host larva have constrained artificial cultivation. In this work, stable carbon isotope analysis was employed to analyse the subsamples of C. sinensis from 5 representative habitats. The results demonstrated that these samples possessed similar δ¹³C profiles, i.e., a steady ascending trend from the top to the bottom of stroma, occurrence of the δ¹³C maximum at the head, a slight decrease from the head to the end of thorax, a sharply descent trend from the end of thorax to the forepart of abdomen, and maintenance of lower δ¹³C values in the rest parts of abdomen. Based on the data, we consider that the site near the head of the host larva may be the initial target attacked by O. sinensis, and the fungus growth is closely related to the digestive tract of its host larva. The growth stages of O. sinensis are accordingly speculated as the symptom-free, symptom-appearing, and stroma-germinating stages.

Better One-Eyed than Blind--Challenges and Opportunities of Biomass Measurement During Solid-State Fermentation of Basidiomycetes

Filamentous fungi, especially basidiomycetes, produce a wide range of metabolites, many of which have potential biotechnological and industrial applications. Solid-state fermentation (SSF) is very suitable for the cultivation of basidiomycetes since it mimics the natural habitat of these fungi. Some of the major advantages of SSF are the robustness of the process, the use of low-cost residual materials as substrates, and the reduced usage of water. However, monitoring key variables is difficult, which makes process control a challenge. Specifically, it is very difficult to determine the biomass during SSF process involving basidiomycetes. This is problematic, as the biomass is normally a key variable in mass and energy balance equations. Further, the success of fungal SSF processes is often evaluated, in part, based on the growth of the fungus. Direct determination of the dry weight of biomass is impossible and indirect quantification techniques must be used. Over the years, various determination techniques have been developed for the quantification of fungal biomass in SSF processes. The current review gives an overview of various direct and indirect biomass determination methods, discussing their advantages and disadvantages.