Influência da concentração do substrato e pH inicial sobre a produção microbiana de lasiodiplodana em meio a base de melaço de soja

Abstract

β-Glucans are polysaccharides that constitute the cell wall of some fungi, yeast and cereals. Commercially, most β-glucans have been extracted from the yeast and cereal cell wall, however, some can be produced and secreted into the extracellular medium by microorganisms cultured in submerged systems. Among the extracellular β- Glucans stands out the lasiodiplodan, which is a (1→6)-β-D-glucan produced by Lasiodiplodia theobromae MMPI. This fungus has been cited as an efficient lasiodiplodan producer using culture media containing glucose, maltose and sucrose. However, the use of alternative carbon sources could reduce the cost of production. In this sense, soybean molasses, a co-product of the soy protein concentrate production process, has demonstrated potential as substrate for the different bioproducts production due to the high sugar’s concentrations. This work aimed the use of soybean molasses as an alternative substrate for lasiodiplodan production by L. theobromae MMPI fungus. Experiments based on full factorial Design (22) were used to evaluate the effect of substrate concentration and initial pH on the lasiodiplodan production and yield and mycelial growth. Kinetic study was conducted to determine the process time by using of the optimized conditions for substrate concentration and initial pH. The substrate concentration variable had a linear negative effect on lasiodiplodan yield (YP/S), and positive linear effect on the cellular biomass production (PX) at 95% confidence level. The pH values studied did not show a significant effect (p<0.05) on the fermentation parameters. Higher values of lasiodiplodan production (1.653 g/L) and yield (0.115 g/g) and higher yield in cell biomass (0.573 g / g) were obtained when using substrate concentration of 20 g/L and initial pH adjusted on 4. Higher substrate concentrations (60 g/L and pH 4) promoted higher cell growth (13.627 g/L). In the kinetic study, the maximum lasiodiplodan production (0.89 g/L) and biomass (7.33 g/L) were observed after 96 hours of cultivation, consuming more than 80% of the substrate. Soybean molasses proved to be an efficient, low cost and alternative substrate for lasiodiplodan and cell biomass production from the submerged culture of the L. theobromae MMPI fungus.