Seleção de leveduras produtoras de trealose e otimização da produção utilizando estrategias sequenciais de planejamento experimental / Screening for trehalose producing yeasts and optimization of production following a sequential strategy of experimental design

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Trehalose is a natural cell-protecting agent that has been isolated and characterized from a large variety of plants, insects, fungi and bacteria, and many studies indicate that this disaccharide is an essential component for maintaining cell viability under stress conditions. Due to the potential application of trehalose, especially in cosmetics and pharmaceuticals fields, the interest of many research groups into the development of economically feasible production systems has increased in recent years. The present study reports on the screening for high trehalose production by yeasts and the optimization of the conditions for trehalose production using an industrial medium composed by molasses and corn steep liquor, to reduce costs of the cultivation medium. Initially, a technical screening was applied to select yeasts with a potential for trehalose production; strains isolated from pollen of flowers and fruits collected in different microhabitats in Brazil, and from alcoholic fermentation tanks were tested. Two potentially producing strains were selected and identified as Rhodotorula dairenensis and Rhodosporidium paludigenum, both isolated from flowers collected in Cerrado. Sequentially, a study for the cell growth optimization of the selected yeasts was performed, since trehalose is an intracellular product. A sequential strategy of experimental design was used; initially, the effects of the concentrations of sugar cane molasses, corn steep liquor and a commercial yeast extract Prodex Lac SD®, and of pH and temperature on the biomass were studied using a fractional design, which was followed by a central composite rotatable design (CCRD). For the yeast Rhodotorula dairenensis, the optimum values for cell growth were 50 g/L for the molasses and corn steep liquor concentrations, initial pH of 5.5 and temperature of 30 ºC, with no yeast extract, reaching values around 19 g/L for biomass. For the yeast Rhodosporidium paludigenum, biomass concentration obtained was 31 g/L in cultivation medium containing 50 g/L of molasses and 140g/L of corn steep liquor, initial pH of 5.5 and temperature of 25 ºC, with no yeast extract. Under these conditions, the production of trehalose was studied using a CCRD to optimize the temperature (33 to 47 ºC) and exposition time (60 to 120 minutes) of the cultures to the thermal stress. For both strains studied, the variable temperature presented a negative effect on trehalose accumulation, in the range studied. In conditions of temperature above 40 ºC there was a decrease of the cell growth and cell viability and, consequently, a decrease of trehalose yields. For the yeast Rhodotorula dairenensis the maximum intracellular trehalose content reached was 18% (g trehalose/100g dry cell) at temperatures of 34 and 35 ºC and between 70 and 90 min of exposition time to the thermal stress. For the strain Rhodosporidium paludigenum the statistical methodology led to maximum contents of intracellular trehalose in the range of 14 -16% (g trehalose/100g dry cell) under thermal stress temperatures of 35 - 40 ºC in all exposition time to the thermal stress in the range studied

ASSUNTO(S)

planejamento experimental experimental design estresse termico trehalose production leveduras substratos industriais thermal stress trealose - produção yeasts raw materials

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