Utilization of stillages from bioethanol production on various substrates

Stillage is a main by-product of the bioethanol industry and, depending on the origin of substrates for bioethanol production, it can be a significant pollutant affecting the profitability of bioethanol production. Directing the stillage towards the production of bio-based chemicals or high-quality feed is a preferred strategy. In this paper, a complete utilization of stillages of different origins was assessed. Thin stillages from bioethanol production from molasses, wasted bread and corn were chemically characterized, evaluated and compared as substrates for lactic acid (LA) and probiotic biomass production by Lactobacillus rhamnosus ATCC 7469, while solid fractions of wasted bread and corn stillages were analyzed for feed. The impact of pH control using CaCO3 or NaOH was also examined, both in terms of LA production and valorization of the remains generated in each process.A maximal LA productivity of 1.14 g/(L h) was obtained on thin wasted bread stillage with pH control by NaOH while the number of viable probiotic bacterial cells was above 109 CFU/mL. The composition of the solid fraction of the wasted bread stillage was complementary with the needs of monogastric animals, while the solid fraction of corn stillage was more adequate for the nutritional requirements of ruminants.

Optimisation of medium composition for probiotic biomass production using response surface methodology

This study was aimed to optimise lactose, inulin and yeast extract concentration and also culture pH for maximising the growth of a probiotic bacterium,Bifidobacterium animalissubsp.lactisin apple juice and to assess the effects of these factors by using response surface methodology. A second-order central composite design was applied to evaluate the effects of these independent variables on growth of the microorganism. A polynomial regression model with cubic and quadratic terms was used for analysis of the experimental data. It was found that the effects involving inulin, yeast extract and pH on growth of the bacterium were significant, and the strongest effect was given by the yeast extract concentration. Estimated optimum conditions of the factors on the bacterial growth are as follows: lactose concentration=9·5 g/l; inulin concentration=38·5 mg/l; yeast extract concentration=9·6 g/l and initial pH=6·2.