Produção de exopolissacarídeos pela levedura Cryptococcus laurentii SD7 utilizando subprodutos agroindustriais

Abstract

Exopolysaccharides (EPS) are extracellular biopolymers produced by microorganisms that are bound to the cell wall or excreted in the form of mucus extracellular medium and can be perceived by increasing the viscosity of the culture medium. EPS has applications in the pharmaceutical, cosmetics, food industry, among others, due to its physicochemical properties. However, the high cost of production of EPS has led to research using alternative substrates, especially renewable and agroindustrial. In this way, this work had as objective to study the production of EPS by yeast Cryptococcus laurentii SD7 using agroindustrial byproducts. For this, fermentation tests were carried out using the rotational central composite (DCCR) 23 design to optimize the EPS production process in different concentrations of sugarcane molasses and corn steep liquor, with pH variation, for 48 hours. After that, fermentation assays were performed for EPS, cell growth and pH variation of the medium at 6, 12, 24, 48, 72, 96, 120, 144 and 168 hours. According to the results, the highest EPS production occurred at the initial pH of 5 and sugarcane molasses concentration 8.4%, with the variables being statistically significant at the 10% level of significance. The corn steep liquor concentration had no influence on the studied range, and it was possible to use the lowest concentration (0.3%). Although cell growth reached its maximum in 48 hours, the highest production of EPS (6.61 g / L) occurred in the time of 168 hours, with a yield of about 0.04 g / L / h and pH of the medium remained constant throughout the fermentation process. Thus, we can conclude that the yeast presented high EPS production and the use of sugarcane molasses and corn steep liquor as substrates proved to be very promising.