| A strain of Penicillium sp. PT95 was isolated from soil sample collected close to Fenyang, Shanxi Province. The strain could form abundant orange, sand-shaped sclerotia in which carotenoid was accumulated. The strain could also form exudates on the colony surface during the development of sclerotia. In the zone where sclerotia formed, there was a compact mass of mycelia on which quantities exudates were present. Physiological and biochemical properties of exudates from Penicillium sp. PT95 were studied. The results showed the exudates were pale yellow as the culture time was prolonged. At 10 days a lot of exudates were present, and at 13 days the exudates were fewer. The pH of exudates varied from 5 to 6. The exudates were found to contain cations, ammonia, protein, glucose and various enzymes. In aging cultures the dry matter weight, total protein, free ammonia, cations(K+, Na+, Cl-, P3+ and Mg2+) decreased whereas Fe2+ and acid phosphatase of the exudates increased. Trehalase, β -glucosidase, polygalacturonase and alkaline phosphatase activities were not detected.The growth of PT95 strain was different in different medium. It can generate quantities exudates and sclerotia in Czapek agar (CA) medium whereas hardly generate exudates both in potato dextrose agar (PDA) medium and Sobouraud agar (SA) medium. In studying the effects of carton and nitrogen sources, carton/nitrogen and kinds of cations on exudates, it could be suggested that the most exudates and sclerotia were obtained when keeping glucose or maltose as the sole carbon source while the content of carotenoid in sclerotia of PT95 strain was biggest when keeping sucrose as the sole carbon source. When keeping soluble starch as the sole carbon source, fewer exudates and more sclerotia could be obtained. Among 8 nitrogen sources, only NaNO3 could make colony produce exudates. Despite the fact that four organic nitrogen sources could not make colony product exudates, they did not affect the sclerotia biomass and the accumulation of carotenoid in sclerotia. The medium containing 0.24 g/L 0.48 g/L sodiumnitrate-nitrogen was effective to both the sclerotial formation and the carotenoid production of strain PT95 when available sucrose -carbon concentrations were at 10.03 g/L 21.05 g/L. The optimal C/N ratio was found to be 25:1. Among inorganic salts tested, K2HP04was more essential to the sclerotial formation and carotenogenesis of strain PT95 than KC1, MgSO4 or FeSO4. MgSO4 could cause quantities exudates and inhibit spore production. Only when the concentration of K2HPO4 was at 0.035 g/L 0.28 g/L and that of MgSO4 at 0.005g/L 0.14 g/L could it form much sclerotia and accumulate more carotenoid accompanied by quantities exudates.The impact of exudate-depletion at sclerotial development stage on the weight, size, biomass of sclerotia and carotenoid accumulation in sclerotia were studied. The results showed that exudate-depletion stimulated the exudation of PT95 strain. Removing exudates made the weight and size of sclerotia decrease and made sclerotia biomass increase after 21 days. The earlier time of exudates removed, the more the sclerotia biomass obtained after 21 days. However, it had little effect on the content of carotenoid in sclerotia. It is enlightened that in order to attain higher sclerotia biomass and carotenoid yield, PT95 strain should be grown under exudate-depletion.We also studied the influence of high oxidative stress growth conditions on the change of exudates and carotenoid accumulation in sclerotia in PT95 strain. The result showed that the daily exudates, sclerotia biomass and the accumulation of carotenoid in sclerotia under light condition were higher than that under dark condition, excepting that of the diameter of colony. As compared with the dark condition, more K+, Na+, Cl", P3+, Mg2+and Fe2+were accumulated in exudates under light condition. When the cultural time prolonged, the concentration of K+, Na+, Cl", P3+ and Mg2+decreased whereas that of Fe2+ increased. The development of sclerotia was always followed by the transition from reduced ascorbic acid to oxidized ascorbic acid in exudates. High oxidative stress growth condition favored the increase of overall ascorbic and the catalase activities in exudates. In addition, the activities of peroxidase and polyphenoloxidase were ten times higher. Byanalyzing of the above experiments, it can easily be found that in unfavorable conditions PT95 strain produced ascorbic acid and antioxidase to remedy deficiency of antioxidation. When ascorbic acid and antioxidase was not sufficient to resist oxidation stress, PT95 strain differentiates to form sclerotia and produce carotenoid to counter ROS formation for long-term survival. It is enlightened that in order to attain higher sclerotia biomass and carotenoid yield, PT95 strain should be grown under high-oxidative stress.
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