Yeast biomass production: a new approach in glucose-limited feeding strategy

Abstract

The aim of this work was to implement experimentally a simple glucose-limited feeding strategy for yeast biomass production in a bubble column reactor based on a spreadsheet simulator suitable for industrial application. In biomass production process using Saccharomyces cerevisiae strains, one of the constraints is the strong tendency of these species to metabolize sugars anaerobically due to catabolite repression, leading to low values of biomass yield on substrate. The usual strategy to control this metabolic tendency is the use of a fed-batch process in which where the sugar source is fed incrementally and total sugar concentration in broth is maintained below a determined value. The simulator presented in this work was developed to control molasses feeding on the basis of a simple theoretical model in which has taken into account the nutritional growth needs of yeast cell and two input data: the theoretical specific growth rate and initial cell biomass. In experimental assay, a commercial baker’s yeast strain and molasses as sugar source were used. Experimental results showed an overall biomass yield on substrate of 0.33, a biomass increase of 6.4 fold and a specific growth rate of 0.165 h−1 in contrast to the predicted value of 0.180 h-1 in the second stage simulation.

Turning industrial aerobic fermentation plants into thermal power stations

“…Produced baker's yeast (845 g on dry matter [DM; Figure 1]) was significantly higher than found in literature. 20,21 Few hours before the end of the fermentation, the dosage of substrates was stopped in order to enable the yeast to accumulate intracellularly energystoring carbohydrates trehalose and glycogen. 22 This led to a slower yeast growth at the end of the fermentation.…”

Fermentation Control in Baker's Yeast Production: Mapping Patents

“…Respiratory quotients were determined as part of various fed‐batch fermentation processes, including baker's yeast and antibiotics manufacturing (Johnson ; Reyman ; Beuermann and others ). In addition to the control of sugar, aeration was a very important limiting factor leading to reduced biomass yields through the production of excessive amounts of ethanol, which may have negative impact on the yeast resistance to stresses during bread manufacturing, including frozen dough (Gélinas and others ; Viera and others ). As recalled by Rolf and Lim (), a small amount of ethanol production during yeast growth is beneficial for acceptable baker's yeast showing high gassing power.…”

Fractionation of baker's yeast vinasse via ultrafiltration: assessment of feasibility

“…The industrial process of baker′s yeast production relies on propagating cells from pure culture agar slants to large bioreactors increasing volume in each propagation stage till the final bioreactor volume (Vieira et al ., ). Usually cane and beet molasses are diluted with water and supply sugars as a source of carbon and organic nitrogen (amino acids, peptides and proteins), minerals, sulphur, vitamins and trace elements.…”

“…production of ethanol under glucose excess even under aerobic conditions), the dosage of sugar must be strictly controlled in order to keep its concentration under 50–100 mg L −1 (Di Serio et al ., ). This can be reached by operating a fed‐batch process (Vieira et al ., ). Downstream processing includes centrifugation to produce a concentrate (yeast cream) with 20% of solids, which is subsequently washed and either pressed or filtered to a semisolid yeast mass of 30% solids (compressed yeast).…”