Nitrogen source and pH interact and modulate lipase secretion in a non-clinical strain of Candida parapsilosis

Lipases (E.C. 3.1.1.3) are serine-hydrolases, and act on long chain fatty acid ester bonds. They exhibit specific and enantioselective activities, which are desirable for many industrial applications. This study aimed at screening and optimizing the production of lipases by wild yeast strains from a variety of substrates, as well as characterizing the enzyme. An initial selection was made in oxygenated oil-supplemented minimum medium, and the enzymatic activity of the supernatant was tested over p-nitrophenyl palmitate. One-hundred and twenty-four yeast strains from different substrates were tested, and twenty-three showed significantly higher lipolytic activity (p<0.01). One yeast in particular, QU110, showed best lipase production and therefore was selected for the optimization and characterization processes. This yeast exhibits enzyme secretion in initial pH 6.0, with olive oil and tryptone as carbon and nitrogen sources, respectively. There was a strong interaction between nitrogen source and initial pH, and pH 9.0seems to inhibit enzyme secretion. The crude enzyme (cell-free supernatant) shows stability in surfactants and n-hexane, but not in ethanol or methanol. A Response Surface Model was created and optimal enzyme activity conditions were observed at 36°C and pH 8.0. The lipase is appropriate for transesterification reactions, as the enzyme is more stable in strong apolar solvents than moderately apolar ones. Also, secretion by pH was not reported elsewhere, which should be further investigated and contribute for other yeast bioprocesses as well.

Comparative growth of trichoderma strains in different nutritional sources, using bioscreen c automated system / Crescimento de linhagens de Trichoderma em diferentes fontes nutricionais, empregando o sistema automatizado Bioscreen C

Trichoderma is one of the fungi genera that produce important metabolites for industry. The growth of these organisms is a consequence of the nutritional sources used as also of the physical conditions employed to cultivate them. In this work, the automated Bioscreen C system was used to evaluate the influence of different nutritional sources on the growth of Trichoderma strains (T. hamatum, T. harzianum, T. viride, andT. longibrachiatum) isolated from the soil in the Juréia-Itatins Ecological Station (JIES), São Paulo State - Brazil. The cultures were grown in liquid culture media containing different carbon- (2%; w/v) and nitrogen (1%; w/v) sources at 28ºC, pH 6.5, and agitated at 150 rpm for 72 h. The results showed, as expected, that glucose is superior to sucrose as a growth-stimulating carbon source in the Trichoderma strains studied, while yeast extract and tryptone were good growth-stimulating nitrogen sources in the cultivation of T. hamatum and T. harzianum.

Trichoderma é um dos gêneros de fungos produtores de metabólitos de interesse industrial. O crescimento destes organismos é conseqüência das fontes nutricionais utilizadas, juntamente com as condições físicas de cultivo. Neste trabalho, o sistema automatizado Bioscreen C foi utilizado para avaliar a influência de diferentes fontes nutricionais sobre o crescimentode linhagens de Trichoderma (T. hamatum, T. harzianum, T. viride e T. longibrachiatum) isoladas do solo da Estação Ecológica da Juréia-Itatins (JIES), São Paulo - Brasil. Os cultivosforam feitos em meios líquidos de cultura contendo diferentes fontes de carbono (2%; w / v) e nitrogênio (1%; w / v) a 28ºC, pH 6,5 e agitados a 150 rpm durante 72 h. Os resultados mostraram, conforme esperado, que a glicose é melhor do que a sacarose como fonte de carbono indutora de crescimento das linhagens de Trichoderma testadas, enquanto que, o extrato de leveduras e a triptona foram boas fontes de nitrogênio indutorasde crescimento para os cultivos de T. hamatum e T. harzianum.

Variation in the molecular weight of Photobacterium damselae subsp. piscicida antigens when cultured under different conditions in vitro

The antigenicity of Photobacterium damselae (Ph. d.)subsp. piscicida, cultured in four different growth media[tryptone soya broth (TSB), glucose-rich medium (GRM),iron-depleted TSB (TSB+IR-), and iron-depleted GRM(GRM+IR-)] was compared by enzyme-linked immuno-sorbent assay (ELISA) and Western blot analysis usingsera obtained from sea bass (Dicentrarchus labrax) raisedagainst live or heat-killed Ph. d. subsp. piscicida. Theantigenic expression of Ph. d. subsp. piscicida was found todiffer depending on the culture medium used. A significantlyhigher antibody response was obtained with iron-depletedbacteria by ELISA compared with non-iron depletedbacteria obtained from the sera of sea bass raised againstlive Ph. d. subsp. piscicida. The sera from sea bass raisedagainst live bacteria showed a band at 22kDa in bacteriacultured in TSB+IR- or GRM+IR- when bacteria thathad been freshly isolated from fish were used for thescreening, while bands at 24 and 47kDa were observedwith bacteria cultured in TSB or GRM. When bacteriawere passaged several times on tryptic soya agar prior toculturing in the four different media, only bands at 24 and47kDa were recognized, regardless of the medium used toculture the bacteria. It would appear that the molecularweight of Ph. d. subsp. piscicida antigens change in thepresence of iron restriction, and sera from sea bassinfected with live bacteria are able to detect epitopes onthe antigens after this shift in molecular weight.