Yeast extract from marine-derived Pichia guilliermondii with different cell wall disruption methods and its application

Abstract: Marine yeasts have been attracting more and more attention as an important resource. In this present, the strain Pichia guilliermondii SY-19 isolated from mangrove sediment was cultured in the liquid medium, and the yeast cells were collected for preparing cell suspensions at concentrations of 5%, 7.5% and 10% (w/w). Then the yeast cell suspensions were subjected to disruption treatment for 12 h with snailase, bienzymes with mannanase and glucanase, and hot alkali, respectively. The percentages of cell disruption and these extracts were calculated after the density of yeast cells and the contents of polysaccharides, protein, amino nitrogen and nucleic acid were detected at 3 h intervals, to select a suitable method for prepartion of yeast extract . And shrimps subjected to ammonia and nitrite stress for 2 weeks were fed for 3 weeks on a diet with no yeast (NY), yeast cells (YC), and yeast extract (YE), then the survive rate and growth performance of shrimps were compared among NY, YC and YE. The results showed that the cell suspensions exhibited the highest rate of cell disruption rate and nucleic acids content, poorer stability of nutrients with hot alkali extraction, the greatest yield percentages of protein, amino nitrogen and polysaccharides, better nutrient retention with bienzymes treatment. Yeast extract as additive was obtained by bienzymes treatment from cell suspensions at concentrations of 5% for 12 h (optimum condition). After 3 weeks, the highest survive rate and final weight of shrimps was obtained in YE (77.674.62%, 2.790.11g) than YC (62.009.90%, 2.440.16 g) and NY (53.6712.91%, 2.190.02 g), significantly different among all groups in survive rate (p0.05), remarkably diferent between YE and NY in final weight (p0.05). These results implied great potential practical application of the strain Pichia guilliermondii SY-19 in shrimp culture.