Changes in Gene Expression of Commercial Baker's Yeast during an Air-Drying Process that Simulates Dried Yeast Production

Scaling up bioprocesses is one of the most crucial steps in the commercialization of bioproducts. While it is known that concentration and shear rate gradients occur at larger scales, it is often too risky, if feasible at all, to conduct validation experiments at such scales. Using computational fluid dynamics equipped with mechanistic biochemical engineering knowledge of the process, it is possible to simulate such gradients. In this work, concentration profiles for the by-products of baker’s yeast production are investigated. By applying a mechanistic black-box model, concentration heterogeneities for oxygen, glucose, ethanol, and carbon dioxide are evaluated. The results suggest that, although at low concentrations, ethanol is consumed in more than 90% of the tank volume, which prevents cell starvation, even when glucose is virtually depleted. Moreover, long exposure to high dissolved carbon dioxide levels is predicted. Two biomass concentrations, i.e., 10 and 25 g/L, are considered where, in the former, ethanol production is solely because of overflow metabolism while, in the latter, 10% of the ethanol formation is due to dissolved oxygen limitation. This method facilitates the prediction of the living conditions of the microorganism and its utilization to address the limitations via change of strain or bioreactor design or operation conditions. The outcome can also be of value to design a representative scale-down reactor to facilitate strain studies.

Download Full-text

Integrated biological (anaerobic–aerobic) and physico-chemical treatment of baker's yeast wastewater

Water Science & Technology ◽

10.2166/wst.2005.0703 ◽

2005 ◽

Vol 52 (10-11) ◽

pp. 273-280 ◽

Cited By ~ 14

Author(s):

S. Kalyuzhnyi ◽

M. Gladchenko ◽

E. Starostina ◽

S. Shcherbakov ◽

B. Versprille

Keyword(s):

Separation Process ◽

Baker’S Yeast ◽

Uasb Reactor ◽

Baker's Yeast ◽

Organic Loading ◽

Cultivation Medium ◽

Loading Rates ◽

Physico Chemical ◽

Yeast Production ◽

Yeast Wastewater

The UASB reactor (35°C) was quite efficient for removal of bulk COD (52–74%) from simulated (on the basis of cultivation medium from the first separation process) general effluent of baker's yeast production (the average organic loading rates varied from 8.1 to 16g COD/l/d). The aerobic-anoxic biofilter (19–23°C) can be used for removal of remaining BOD and ammonia from anaerobic effluents; however, it suffered from COD-deficiency to fulfil denitrification requirements. To balance COD/N ratio, some bypass (∼10%) of anaerobically untreated general effluent should be added to the biofilter feed. The application of iron (III)-, aluminium- or calcium-induced coagulation for post-treatment of aerobic-anoxic effluents can fulfil the limits for discharge to sewerage (even for colour mainly exerted by hardly biodegradable melanoidins), however, the required amounts of coagulants were relatively high.

Download Full-text

Macroscopic modelling of baker's yeast production in fed-batch cultures and its link with trehalose production

Computers & Chemical Engineering ◽

10.1016/j.compchemeng.2013.11.007 ◽

2014 ◽

Vol 61 ◽

pp. 220-233 ◽

Cited By ~ 9

Author(s):

Anne Richelle ◽

Patrick Fickers ◽

Philippe Bogaerts

Keyword(s):

Baker’S Yeast ◽

Baker's Yeast ◽

Fed Batch ◽

Batch Cultures ◽

Yeast Production

Download Full-text

Validation of a Flour-Free Model Dough System for Throughput Studies of Baker's Yeast

Applied and Environmental Microbiology ◽

10.1128/aem.71.3.1142-1147.2005 ◽

2005 ◽

Vol 71 (3) ◽

pp. 1142-1147 ◽

Cited By ~ 28

Author(s):

Joaquin Panadero ◽

Francisca Randez-Gil ◽

Jose Antonio Prieto

Keyword(s):

Gene Expression ◽

Sugar Content ◽

Transcriptional Response ◽

Northern Blotting ◽

Baker’S Yeast ◽

Marker Genes ◽

Mrna Levels ◽

Baker's Yeast ◽

High Sugar ◽

High Sugar Content

ABSTRACT Evaluation of gene expression in baker's yeast requires the extraction and collection of pure samples of RNA. However, in bread dough this task is difficult due to the complex composition of the system. We found that a liquid model system can be used to analyze the transcriptional response of industrial strains in dough with a high sugar content. The production levels of CO2 and glycerol by two commercial strains in liquid and flour-based doughs were correlated. We extracted total RNA from both a liquid and a flour-based dough. We used Northern blotting to analyze mRNA levels of three stress marker genes, HSP26, GPD1, and ENA1, and 10 genes in different metabolic subcategories. All 13 genes had the same transcriptional profile in both systems. Hence, the model appears to effectively mimic the environment encountered by baker's yeast in high-sugar dough. The liquid dough can be used to help understand the connections between technological traits and biological functions and to facilitate studies of gene expression under commercially important, but experimentally intractable, conditions.

Download Full-text