Bioavailability of Compounds Susceptible to Enzymatic Oxidation Enhances Growth of Shiitake Medicinal Mushroom (Lentinus edodes) in Solid-State Fermentation with Vineyard Prunings.

Grapes are widely produced in northwestern Mexico, generating many wood trimmings (vineyard prunings) that have no further local use. This makes vineyard prunings a very attractive alternative for the cultivation of white-rot medicinal mushrooms such as Lentinus edodes. This type of wood can also offer a model for the evaluation of oxidative enzyme production during the fermentation process. We tested the effect of wood from vineyard prunings on the vegetative growth of and production of ligninolytic enzymes in L. edodes in solid-state fermentation and with wheat straw as the control substrate. The specific growth rate of the fungus was 2-fold higher on vineyard pruning culture (µM = 0.95 day-1) than on wheat straw culture (µM = 0.47 day-1). Laccase-specific production was 4 times higher in the vineyard prunings culture than on wheat straw (0.34 and 0.08 mU · mg protein-1 · ppm CO2-1, respectively), and manganese peroxidase production was 3.7 times higher on wheat straw culture than on vineyard prunings (2.21 and 0.60 mU · mg protein-1 · ppm CO2-1, respectively). To explain accurately these differences in growth and ligninolytic enzyme activity, methanol extracts were obtained from each substrate and characterized. Resveratrol and catechins were the main compounds identified in vineyard prunings, whereas epigallocatechin was the only one detected in wheat straw. Compounds susceptible to enzymatic oxidation are more bioavailable in vineyard prunings than in wheat straw, and thus the highest L. edodes growth rate is associated with the presence of these compounds.

Isolation of dipicolinic acid as an insecticidal toxin from Paecilomyces fumosoroseus.

Several entomopathogenic fungi produce toxins that could be used as bioinsecticides in integrated pest management programs. Paecilomyces fumosoroseus is currently used for the biological control of the whiteflies Bemisia tabaci and B. argentifolii. Supernatants from submerged batch culture, where the fungus produced abundant dispersed mycelium, conidia and blastospores, were toxic to the whitefly nymphs. The most abundant metabolite was purified by HPLC and identified by mass spectrometry and NMR as dipicolinic acid. Both the dipicolinic acid produced by the fungus and the chemically synthesized compound had insecticidal activity against third-instar nymphs of the insect. Dipicolinic acid was toxic to the whitefly nymphs in bioassays involving topical applications. In submerged culture, the specific growth rate of P. fumosoroseus was 0.054 h-1, the specific glucose consumption rate was 0.1195 g g-1 h-1 and the specific dipicolinic acid production rate was 0.00012 g g-1 h-1. Dipicolinic acid was detected after 24 h when the fungus started growing; and dipicolinic acid production was directly correlated with fungal growth. Nevertheless, the yield was low and the maximal concentration was only 0.041 g l-1. The maximal concentrations of conidia and blastospores (per milliliter) were 1.4x10(8) and 7x10(7), respectively.