Phenotypic evaluation of natural and industrial Saccharomyces yeasts for different traits desirable in industrial bioethanol production

Abstract

Saccharomyces cerevisiae is the organism of choice for many food and beverage fermentations because it thrives in high-sugar and high-ethanol conditions. However, the conditions encountered in bioethanol fermentation pose specific challenges, including extremely high sugar and ethanol concentrations, high temperature, and the presence of specific toxic compounds. It is generally considered that exploring the natural biodiversity of Saccharomyces strains may be an interesting route to find superior bioethanol strains and may also improve our understanding of the challenges faced by yeast cells during bioethanol fermentation. In this study, we phenotypically evaluated a large collection of diverse Saccharomyces strains on six selective traits relevant for bioethanol production with increasing stress intensity. Our results demonstrate a remarkably large phenotypic diversity among different Saccharomyces species and among S. cerevisiae strains from different origins. Currently applied bioethanol strains showed a high tolerance to many of these relevant traits, but several other natural and industrial S. cerevisiae strains outcompeted the bioethanol strains for specific traits. These multitolerant strains performed well in fermentation experiments mimicking industrial bioethanol production. Together, our results illustrate the potential of phenotyping the natural biodiversity of yeasts to find superior industrial strains that may be used in bioethanol production or can be used as a basis for further strain improvement through genetic engineering, experimental evolution, or breeding. Additionally, our study provides a basis for new insights into the relationships between tolerance to different stressors.

A Large Set of Newly Created Interspecific Saccharomyces Hybrids Increases Aromatic Diversity in Lager Beers

“…Careful selection of optimal parental strains is vital for successful breeding experiments. Previously, our research group screened 301 industrial and wild strains from a large Saccharomyces yeast collection for different industrially relevant traits (22,33,43). Based on these data, six S. cerevisiae strains were selected using four selection criteria: production of a diverse aroma profile, high sporulation capacity, high spore viability, and efficient maltose fermentation (Fig.…”

Isolation and Identification of Local Ethanol Tolerant Yeast Populating Distillation and Milling Sites in Nigeria

“…The colour change observed (red to yellow) was indicative of the presence of an array of organic acids which may include phytic acid, a compound recently reported to be produced by Pichia species and a number of other non-Saccharomyces yeasts including Arxula adeninivorans, Candida krusei, Cryptococcus laurentii, Debaryomyces castellii, Debaryomyces occidentalis, Pichia sp., Rhodotorula gracilis, Schwanniomyces castellii, etc which aids in the release of phosphorus compounds from organic sources in the soil [21]. This observation suggests that the culture organisms possess good fermentative capabilities.…”

On-line identification of fermentation processes for ethanol production

“…Enzyme feed rate profiles were provided as functions of time, assuming that F enz (flow rate of the enzyme feed stream) and C enz E (enzyme concentration of the enzyme feed stream) were known, as specified in Eq. (18). The lumped reaction rate constants (parameters k H1 , k H2 and k H3 in Equations 1-3) were estimated with the available process outputs, as discussed previously.…”

“…In general, enhanced bioprocess operation and greater profitability are accomplished through increased feedstock quality [15], phenotype improvement of cell lines [16][17][18], and process systems engineering tools, such as techniques for monitoring, control, and optimization [19]. Despite the presence and application of the first two, the later is always present to some extent.…”