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Truffle ( Tuber spp.), also known as 'underground gold,' is popular in various cuisines because of its unique and characteristic aroma. Currently, truffle fruiting bodies are mostly obtained from nature and semi-artificial cultivation. However, the former source is scarce, and the latter is time-consuming, usually taking 4 to 12 years before harvest of the fruiting body. The truffle submerged fermentation process was first developed in Tang's lab as an alternative to its fruiting bodies. To the best of our knowledge, most reports of truffle submerged fermentation come from Tang's group. This review examines the current state of the truffle submerged fermentation process. First, the strategy to optimize the truffle submerged fermentation process is summarized; the final conditions yielded not only the highest reported truffle biomass but also the highest production of extracellular and intracellular polysaccharides. Second, the comparison of metabolites produced by truffle fermentation and fruiting bodies is presented, and the former were superior to the latter. Third, metabolites (i.e., volatile organic compounds, equivalent umami concentration, and sterol) derived from truffle fermentation could be regulated by fermentation process optimization. These findings indicated that submerged fermentation of truffles can be used for commercial production of biomass and metabolites as a promising alternative to generating its fruiting bodies in bioreactor. [ABSTRACT FROM AUTHOR]

Abstract: Truffles are hypogeous ascomycetes and ectomycorrhizal fungi with unique organoleptic properties. Effects of nitrogen source and its concentration were studied during the submerged fermentation of Chinese truffle Tuber sinense. Yeast extract was identified to be the most favorable for the cell growth, and the next was peptone. The maximal dry cell weight of 19.53±0.13g/L obtained at an initial yeast extract concentration of 25g/L was higher by 40.9% compared to that at 10g/L. Within the range of initial peptone concentration (i.e., 10, 20, 30 and 40g/L) as investigated, the maximal biomass and the production of extracellular polysaccharide (EPS) were obtained at 30g/L, while 20g/L was favorable for the production of intracellular polysaccharide (IPS). A mathematical model, which was constructed by response surface methodology combination with Box-Behnken design (BBD), was applied to study the synergic effect of glucose, yeast extract and peptone. According to the model prediction, the optimal initial concentration of glucose, yeast extract and peptone was 60, 30 and 10g/L, respectively. The validation experiment showed the experimental values agreed with the predicted values well. The highest biomass (i.e., 23.94±0.49g/L), the production of EPS (i.e., 1.59±0.06g/L) and IPS (i.e., 1.48±0.26g/L) were obtained under the predicted optimal conditions, which were higher by 22.6%, 42.0% and 16.5% compared with the best results of one-variable-at-a-time experiments, respectively. [Copyright &y& Elsevier]

Abstract: During the submerged fermentation of medicinal mushroom Chinese truffle Tuber sinense, there was no significant effect of metal ion on the cell growth and the production of intracellular polysaccharides, while metal ion and its concentration significantly affected the production of extracellular polysaccharides (EPS). By using the approach of “one-variable-at-a-time”, 50mM Mg2+ was identified to be the most favorable for EPS production, and the next was 10mM K+. A mathematical model, constructed by response surface methodology combination with full factorial design, was applied to study the synergic effect of Mg2+ and K+. EPS production reached its peak value of 5.86g/L under their optimal combination of 30mM Mg2+ and 5mM K+ predicted by the model, which was higher by 130.7% compared with the basal fermentation medium without metal ion. The validation experiment showed the experimental values agreed with the predicted values well. EPS production obtained in this work was the highest reported in the culture of T. sinense. [Copyright &y& Elsevier]