Alcoholic Fermentation with Flocculant Saccharomyces cerevisiae in Fed-Batch Process

Abstract

Studies have been conducted on selecting yeast strains for use in fermentation for ethanol production to improve the performance of industrial plants and decrease production costs. In this paper, we study alcoholic fermentation in a fed-batch process using a Saccharomyces cerevisiae yeast strain with flocculant characteristics. Central composite design (CCD) was used to determine the optimal combination of the variables involved, with the sucrose concentration of 170 g/L, a cellular concentration in the inoculum of 40% (v/v), and a filling time of 6 h, which resulted in a 92.20% yield relative to the theoretical maximum yield, a productivity of 6.01 g/L h and a residual sucrose concentration of 44.33 g/L. With some changes in the process such as recirculation of medium during the fermentation process and increase in cellular concentration in the inoculum after use of the CCD was possible to reduce the residual sucrose concentration to 2.8 g/L in 9 h of fermentation and increase yield and productivity for 92.75% and 9.26 g/L h, respectively. A model was developed to describe the inhibition of alcoholic fermentation kinetics by the substrate and the product. The maximum specific growth rate was 0.103 h(-1), with K(I) and K(s) values of 109.86 and 30.24 g/L, respectively. The experimental results from the fed-batch reactor show a good fit with the proposed model, resulting in a maximum growth rate of 0.080 h(-1).

Kinetic Modeling and Optimization of a Batch Ethanol Fermentation Process

“…In particular, the value of Y P/S is close to those reported by Guidini et al [14] for five strains of flocculating yeasts identified as Saccharomyces cerevisiae. On the other hand, the value of α agrees well with that published by Nelson and Hamzah [15] for the parameter Y X/P (=0.235 g/g), the reciprocal of α, i.e., Y X/P =1/α.…”

Kinetic Modeling of 1‐G Ethanol Fermentations

“…Since ethanol is a product of the primary metabolism of the yeasts, the majority of described cases assumes α > 0 and β = 0, as reported by Oliveira et al [19] when they modeled the batch ethanol production, using the expression μ P = αμ X , with α = 4.17 g/g. However, it is possible to find descriptions in the literature of ethanol production, parts associated and not associated with cell growth, that is, α > 0 and β > 0, as is the case with that reported by Guidini et al [18] that used the following equation to describe μ P in a fedbatch ethanol fermentation process with flocculating yeasts (S. cerevisiae):…”

“…The inhibition caused by the excess of substrate has generally been modeled by applying the Andrews equation [16][17][18][19], though there are other types of equations that are less commonly used [20].…”

“…(36) [18] Oliveira et al [57], modeling a continuous ethanol fermentation process in a two-stage tower bioreactor cascade with flocculating yeast recycle, used simplified (μ S = μ P /Y P/S ) and general-…”

Avaliação das condições de processo na resistência da levedura ao teor final de etanol na fermentação alcoólica

“…Figura 4.7 -Curvas de contorno para a resposta rendimento avaliando as variáveis temperatura, concentração celular no inóculo, concentração ART na alimentação e tempo de enchimento do reator duas a duas. Guidini et al (2013), com a cepa C2/00 obteve rendimento de 93,9%, utilizando 153 g/L de ART, concentração celular de 15 g/L, tempo de enchimento do reator de 6 horas e temperatura do processo fermentativo de 32°C. Para esta mesma fermentação foi obtido produtividade de 4,27 g etanol /L.h e restou ao final de 10,5 horas de fermentação 56,3 g de sacarose residual.…”