Effect of cultivation conditions on cellulase activity of higher fungi.

Production of cellulases was followed in 4 cultures of higher fungi (Agrocybe cylindracea, Len tinus tigrinus, Pleurotus ostreatus, Ramaria formosa) cultivated on various substrates under different conditions. Stationary cultivation was more suitable than the submerged one. Addition of carboxymethy cellulose (CMC) was more suitable than addition of glucose. The cellulase activity in the presence of CMC was higher after a 12-d cultivation than after a 23-d period. Pine sawdust was most effective of all the substrates tested for the production of cellulases. Beech sawdust and wheat or rye straw were also useful. The addition of yeast autolyzate decreased the production of cellulases. A culture of L. tigrinud was the best producer.

Utilization of fat and degradation of cholesterol by Pleurotus spp.

Plant oil was found to stimulate the formation of biomass in Pleurotus ostreatus, P. ostreatus from Florida and P. cornucopiae. The highest increase of the delipidized dry substance was found in P. ostreatus. The supernatant after submerged fermentation contained active emulsifiers. Fruiting bodies and mycelium of P. ostreatus did not contain cholesterol. Cholesterol added to homogenates of the fruiting bodies was degraded in a temperature-dependent manner. Degradation of cholesterol in the fermentation medium was slower.

Cellulase activity of higher fungi.

The method of liquefaction of gel from cross-linked cellulose was used for monitoring the cellulolytic activity of 114 cultures of higher fungi, 47 of which belonged to Pleurotus ostreatus. All cultures of P. ostreatus had a low activity. The highest cellulase activity, manifested by Piptoporus betulinus, was comparable with that of Tricloderma viride QM6a.

The relationship between Pleurotus ostreatus and Aspergillus flavus and the production of aflatoxin.

The relationship between Pleurotus ostreatus and Aspergillus flavus in common mixed culture on various substrates was investiaged. It was found that P. Ostreatus, similarly to some other higher fungi, can liquidate colonies of A. flavus. This fungus does not produce aflatoxin and chromatographically similar compounds. On straw, corn cobs, millet and wheat A. flavus produced aflatoxin after a 3-week cultivation. A subsequent cultivation of P. ostreatus led to detoxication of straw and corn cobs but millet and wheat were not detoxicated. Cultivation of P. osteatus in the presence of 40-100 micrograms of aflatoxin B1 per g substrate did not result in detoxication of the material even after 34 d but the results showed that the aflatoxin concentration decreased to about one-fourth of the added amount.

A simple method of isolation and purification of cultures of wood-rotting fungi.

A simple method of isolation and purification of cultures of higher fungi, mainly wood-rotting fungi, without special requirements for the presence of nitrogencontaining nutrients is described. Parts of fruiting bodies, spores or infected wood is inoculated on Petri dishes with an agar medium of the following composition: 1.0 g KH2PO4, 0.2 g MgSO4 - 7 H2O, 0.1 g caSO4, 0.01 g Fe2(SO4)3, 10.0 g glucose, tap water to 1 litre; 20.0 g agar. This medium does not suit most of the contaminants but fungal hyphae overgrow the whole surface of the dish so that a purified culture can be obtained from parts distant from the inoculation site.

The balance of nitrogen and composition of proteins in Pleurotus ostreatus grown on natural substrates.

The balance of nitrogen and nitrogen compounds in Pleurotus ostreatus, cultivated on waste materials, corn straw and maize residues, was investigated. The results show that this organism has a considerable ability to fix atmospheric nitrogen, fixing 312 g of total nitrogen per 100 kg dry weight. When recalculating with respect to a decrease of the substrate during growth of the organism a value of 9.7 mg per 1 g of the decrease in material is obtained. Fruiting bodies, as well as the produced substrate contain 17-19 amino acids. In the produced substrate the content of the protein nitrogen represents only 30% of the total. It can concluded that Pleurotus ostreatus yields a suitable raw material in the food industry and possibly also a fodder based on the basis of solid, cellulose-containing wastes.