A synthetic medium to simulate sugarcane molasses

Abstract

BackgroundDeveloping novel microbial cell factories requires careful testing of candidates under industrially relevant conditions. However, this frequently occurs late during the strain development process. The availability of laboratory media that simulate industrial-like conditions might improve cell factory development, as they allow for strain construction and testing in the laboratory under more relevant conditions. While sugarcane molasses is one of the most important substrates for the production of biofuels and other bioprocess-based commodities, there are no defined media that faithfully simulate it. In this study, we tested the performance of a new synthetic medium simulating sugarcane molasses.ResultsLaboratory scale simulations of the Brazilian ethanol production process, using both sugarcane molasses and our synthetic molasses (SM), demonstrated good reproducibility of the fermentation performance, using yeast strains, PE-2 and Ethanol Red™. After 4 cycles of fermentation, the final ethanol yield (gp gs−1) values for the SM ranged from 0.43 ± 0.01 to 0.44 ± 0.01 and from 0.40 ± 0.01 to 0.46 ± 0.01 for the molasses-based fermentations. The other fermentation parameters (i.e., biomass production, yeast viability, and glycerol and acetic acid yield) were also within similar value ranges for all the fermentations. Sequential pairwise competition experiments, comparing industrial and laboratory yeast strains, demonstrated the impact of the media on strain fitness. After two sequential cocultivations, the relative abundance of the laboratory yeast strain was 5-fold lower in the SM compared to the yeast extract-peptone-dextrose medium, highlighting the importance of the media composition on strain fitness.ConclusionsSimulating industrial conditions at laboratory scale is a key part of the efficient development of novel microbial cell factories. In this study, we have developed a synthetic medium that simulated industrial sugarcane molasses media. We found good agreement between the synthetic medium and the industrial media in terms of the physiological parameters of the industrial-like fermentations.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1221-x) contains supplementary material, which is available to authorized users.

Physiological characterization of a new thermotolerant yeast strain isolated during Brazilian ethanol production and its application in high temperature fermentation

“…There is insu cient data reported for conditions that reproduce the different characteristics found in industrial environments. Speci cally in Brazilian 1G ethanol production, sugarcane juice and molasses are often used as a lower cost carbon source for fermentation [35]. Its composition and quality also vary among different batches and harvesting periods; therefore, synthetic laboratory medium replicates of conditions are poor and may lead to misinterpreted conclusions [36].…”

“…Ethanol yield for each cycle was calculated as described elsewhere [35]. A correction factor for high cell density was applied as previously reported, and a speci c volume of 0.7 mL g − 1 (wet basis) was considered for yeast cells.…”

“…Fermentation started with the addition of 6 mL of water and 2 mL of the "vinho" to the 50-mL centrifuge tubes containing 4 g of cells. The cells corresponded to 10% w.v − 1 and the remaining "vinho" from the previous step simulated the e ciency of the industrial centrifuge [35]. The fermentation cycle started with the addition of 9.25 mL of fermentation medium (19% TRS sugarcane molasses from usina SJ) to the tubes.…”

Complex yeast-bacteria interactions affect the yield of industrial ethanol fermentations

“…Sugarcane ethanol fermentations with synthetic microbial communities represent a potentially interesting real-world microbial community that is tractable for comprehensive assessment. The microbial community from sugarcane ethanol fermentations is reproducible, and simplified versions can be established in the laboratory [11][12][13] , providing researchers with a wealth of data regarding fermentation parameters that are directly linked to microbial physiology and community functionality (e.g., ethanol titre, biomass growth, and organic acid titres) 11 . Additionally, bioethanol production has both economic and environmental relevance.…”

Bioconversion of poly-γ-glutamic acid (γ-PGA) from fulvic acid powder produced from the wastewater of yeast molasses fermentation

“…primarily sucrose, glucose, and fructose), and is abundant, low-cost and highly available for the fermentation industry [5][6][7]. Thereby, molasses is widely used for microbial conversion into different value-added products, such as bioethanol, baker's yeast, amino acids, butanol, organic acids, single cell proteins, etc [8][9][10][11]. However, the fermentation poses a severe waste disposal problem worldwide [12], because most wastewater is discharged into the environment without appropriate pre-treatment, aggravating the dire water pollution situations, and contributing to severe environmental pollution [1,13,14].…”