Engineering and integration of pathways for anaerobic redox-cofactor balancing in yeast

The production of ethanol by the yeast Saccharomyces cerevisiae remains the process in industrial biotechnology with the largest product volume (ca. 100 million litres annually in 2022). Carbon losses occur due to the formation of biomass and glycerol, which can account for at least 8% of the product. Under anaerobic conditions, formation of...

Quantification and mitigation of byproduct formation by low-glycerol-producing Saccharomyces cerevisiae strains containing Calvin-cycle enzymes

Background: Anaerobic Saccharomyces cerevisiae cultures require glycerol formation to re-oxidize NADH formed in biosynthetic processes. Introduction of the Calvin-cycle enzymes phosphoribulokinase (PRK) and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) has been shown to couple re-oxidation of biosynthetic NADH to ethanol...

Co-cultivation of Saccharomyces cerevisiae strains combines advantages of different metabolic engineering strategies for improved ethanol yield

Glycerol is the major organic byproduct of industrial ethanol production with the yeast Saccharomyces cerevisiae. Improved ethanol yields have been achieved with engineered S. cerevisiae strains in which heterologous pathways replace glycerol formation as the predominant mechanism for anaerobic re-oxidation of surplus NADH generated in...

Optimizing the balance between heterologous acetate- and CO2-reduction pathways in anaerobic cultures of Saccharomyces cerevisiae strains engineered for low-glycerol production

In anaerobic Saccharomyces cerevisiae cultures, NADH (reduced form of nicotinamide adenine dinucleotide)-cofactor balancing by glycerol formation constrains ethanol yields. Introduction of an acetate-to-ethanol reduction pathway based on heterologous acetylating acetaldehyde dehydrogenase (A-ALD) can replace glycerol formation as 'redox-sink'...

An engineered non-oxidative glycolytic bypass based on Calvin-cycle enzymes enables anaerobic co-fermentation of glucose and sorbitol by Saccharomyces cerevisiae

Background: Saccharomyces cerevisiae is intensively used for industrial ethanol production. Its native fermentation pathway enables a maximum product yield of 2 mol of ethanol per mole of glucose. Based on conservation laws, supply of additional electrons could support even higher ethanol yields. However, this option is disallowed by the...

Pathway engineering strategies for improved product yield in yeast-based industrial ethanol production

Product yield on carbohydrate feedstocks is a key performance indicator for industrial ethanol production with the yeast Saccharomyces cerevisiae. This paper reviews pathway engineering strategies for improving ethanol yield on glucose and/or sucrose in anaerobic cultures of this yeast by altering the ratio of ethanol production, yeast growth...

Quality of Care Perceived by Older Patients and Caregivers in Integrated Care Pathways With Interviewing Assistance From a Social Robot: Noninferiority Randomized Controlled Trial

Background: Society is facing a global shortage of 17 million health care workers, along with increasing health care demands from a growing number of older adults. Social robots are being considered as solutions to part of this problem. Objective: Our objective is to evaluate the quality of care perceived by patients and caregivers for an...

Laboratory Evolution of a Saccharomyces cerevisiae × S. eubayanus Hybrid Under Simulated Lager-Brewing Conditions

Saccharomyces pastorianus lager-brewing yeasts are domesticated hybrids of S. cerevisiae x S. eubayanus that display extensive inter-strain chromosome copy number variation and chromosomal recombinations. It is unclear to what extent such genome rearrangements are intrinsic to the domestication of hybrid brewing yeasts and whether they...