Studies On Accumulation Of Lipid In Sclerotia Of Penicillium Sp. PT95

A strain of Penicillium sp. PT95 was isolated from soil sample collected close to Fenyang, Shanxi Province. The strain can form abundant orange, sand-shaped sclerotia in which carotenoid are accumulated. By morphological observation and RAPD typing , PT95 strain had been identified to P. thomii series. The analysis had been done on accumulation of carotenoid in sclerotia. The aim of this paper was studying the effects of various factors on lipid accumulation in sclerotia of PT95 strain on agar media.By comparing growth period, sclerotial biomass, content of lipid and lipid yield of PT95 strain in Czapek agar(CA), potato dextrose agar (PDA) and Joham's nutrient agar media, it was found that light growth condition was favorable to formation of sclerotia and lipid biosynthesis of this fungus. Joham's nutrient agar medium could shorten the growth period and enhance lipid yield of PT95 strain. The highest lipid yield was obtained when glucose was used as carbon source.Studies on the influence of C/N on sclerotial biomass and lipid production of PT95 demonstrated that lipid content and lipid yield remained the highest at a C/N-ratio of 70 : 1 and sclerotial biomass remained the highest at a C/N-ratio of 30 : 1. At C/N-ratios higher than 10 : 1 lipid content and lipid yield of PT95 strain increased gradually until C/N-ratio of 70 : 1.By comparing growth period, sclerotial biomass and lipid content and lipid yield of PT95 strain on media containing different nitrogen sources, it was found that peptone, NaNO₃ and NH4NO₃ were favorable to the formation of sclerotia and lipid biosynthesis of this fungus. Among several nitrogen sources tested, urea, NH₄Cl and (NH₄)₂SO₄ did not support PT95 strain growth under the tested concentrations.The effects of K₂HPO₄ and FeSO₄ on sclerotial biomass, lipid content and lipid yield were studied. The total sclerotial biomass and lipid yield increased with increasing concentration of K₂HPO₄ (0.5g/L¹.0g/L)in the media.However, FeSO4 could inhibit sclerotial differentiation and lipid accumulation. The higher the concentration of FeSO4 was, the stronger the inhibition was.Through orthogonal experiments, the optimum medium was obtained and contained per liter: glucose 157.5g, NH4NO3 l.Og, K2HPO4 0.5g, MgSO4-7H2O 0.2g, KC1 0.14g, FeSO40.002g, ZnCl20.002g, MnCl2 0.002g, thiamin 0.000 lg, agar 20g.Under the optimum culture conditions, the lipid yields reached its maximum values of 173.59mg at the 14th day. The result showed that the influence of the carbon to nitrogen ratio and culture time was obvious and that of K2HPO4 was not obvious.The influence of culture time on sclerotial biomass, lipid content and lipid yield of PT95 strain in optimum medium was studied. The results suggested that lipid accumulation was closely associated with the sclerotial differentiation of PT95. The data showed that sclerotial biomass and lipid yield was increasing until mature periods of sclerotia. PT95 could accumulate highest lipid in sclerotia (41.2%) when grown in optimum medium at the eighth day. The highest lipid yield and highest sclerotial biomass were obtained under optimum medium at the mature periods of sclerotia, reached respectively 178.13 mg and 539 mg per plate. A preliminary analysis on the fatty acid composition was performed. The lipid in sclerotia of PT95 were composed of dodecanoic acid, palmitic acid, stearic acid, ejcosanoic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, eicosenoic acid and eicosadienoic acid.