Revitalizing the ethanologenic bacterium Zymomonas mobilis for sugar reduction in high-sugar-content fruits and commercial products

Abstract

The excessive consumption of sugars can cause health issues. Different strategies have been developed to reduce sugars in the diets. However, sugars in fruits and commercial products may be difficult to reduce, limiting their usage among certain populations of people. Zymomonas mobilis is a generally recognized as safe (GRAS) probiotic bacterium with the capability to produce levan-type prebiotics, and thrives in high-sugar environments with unique characteristics to be developed for lignocellulosic biofuel and biochemical production. In this study, the sugar reduction capabilities of Z. mobilis ZM4 were examined using two fruits of pear and persimmon and three high-sugar-content commercial products of two pear pastes (PPs) and one Chinese traditional wine (CTW). Our results demonstrated that Z. mobilis ZM4 can utilize sugars in fruits with about 20 g/L ethanol and less than 5 g/L sorbitol produced within 22 h using pears, and about 45 g/L ethanol and 30 g/L sorbitol produced within 34 h using persimmons. When PPs made from pears were used, Z. mobilis can utilize nearly all glucose (ca. 60 g/L) and most fructose (110 g/L) within 100 h with 40 ~ 60 g/L ethanol and more than 20 g/L sorbitol produced resulting in a final sorbitol concentration above 80 g/L. In the high-sugar-content alcoholic Chinese traditional wine, which contains mostly glucose and ethanol, Z. mobilis can reduce nearly all sugars with about 30 g/L ethanol produced, resulting in a final ethanol above 90 g/L. The ethanol yield and percentage yield of Z. mobilis in 50 ~ 60% CTW were 0.44 ~ 0.50 g/g and 86 ~ 97%, respectively, which are close to its theoretical yields—especially in 60% CTW. Although the ethanol yield and percentage yield in PPs were lower than those in CTW, they were similar to those in fruits of pears and persimmons with an ethanol yield around 0.30 ~ 0.37 g/g and ethanol percentage yield around 60 ~ 72%, which could be due to the formation of sorbitol and/or levan in the presence of both glucose and fructose. Our study also compared the fermentation performance of the classical ethanologenic yeast Saccharomyces cerevisiae BY4743 to Z. mobilis, with results suggesting that Z. mobilis ZM4 had better performance than that of yeast S. cerevisiae BY4743 given a higher sugar conversion rate and ethanol yield for sugar reduction. This work thus laid a foundation for utilizing the advantages of Z. mobilis in the food industry to reduce sugar concentrations or potentially produce alcoholic prebiotic beverages. Graphical Abstract

Adaptive Laboratory Evolution and Metabolic Engineering of Zymomonas mobilis for Bioethanol Production Using Molasses

“…Even after 100 h fermentation, about 23.56 g/L fructose was still not consumed, and the ethanol titer and biomass were 58.46 g/L and 2.10 OD 600 , respectively (Figure B). The results indicated that glucose was superior to fructose for ethanol fermentation, which is consistent with the earlier report …”

“…The results indicated that glucose was superior to fructose for ethanol fermentation, which is consistent with the earlier report. 41 When sucrose is used as the carbon source, Z. mobilis hydrolyzes sucrose to glucose and fructose and then ferment them to ethanol. 17,40 Z. mobilis 8b hydrolyzed most sucrose in the first 10 h with a significant amount of glucose and fructose detected, which is consistent with the previous report that the catabolic activity of glucose and fructose limited the ethanol formation on sucrose instead of sucrose hydrolysis capability in Z. mobilis.…”

“…Corresponding to the poor sucrose hydrolysis, fewer free glucose and fructose were accumulated during the fermentation process with only 71.71 g/L of total sugar consumed and 31.11 g/L ethanol produced (Figure D). Compared with the fermentation performance with pure sugar glucose, fructose, or sucrose as the carbon source, sucrose hydrolysis as well as the glucose and fructose catabolism impeded the ethanol fermentation in molasses (Figure ), which could be due to the inhibition of sucrose hydrolysis and fructose utilization in the presence of free glucose and potential toxic compounds in molasses as reported before. , …”

Temporal Pattern of Neuroinflammation Associated with a Low Glycemic Index Diet in the 5xFAD Mouse Model of Alzheimer’s Disease

“…It has been proposed that at early stages a prevailing pro-inflammatory process can be treated and reversed, while at later clinical stages, the presence of sustained and excessive brain damage may reciprocally fuel a deregulated innate and adaptive immune response that renders anti-inflammatory treatments largely ineffective [ 74 ]. Furthermore, novel strategies that are being developed to reduce sugars in fruits, such as the use of probiotic bacteria (e.g., Zymomonas mobilis ) that thrive in high-sugar environments and have been shown to reduce the glucose and fructose from fruit pastes [ 75 ], could be also utilized to reduce the sugar-concentration in currant paste as well.…”

Metabolic engineering of Zymomonas mobilis for co-production of D-lactic acid and ethanol using waste feedstocks of molasses and corncob residue hydrolysate

“…Samples from the shake flasks or bioreactors were centrifuged at 13,000 rpm for 2 min and then the supernatants were filtered through a 0.2-μm syringe filter into high-performance liquid chromatography (HPLC) vials. Concentrations of sucrose, glucose, fructose, ethanol, and lactate in the supernatants were then detected by HPLC (Shimadzu, Japan) equipped with a refractive index detector (RID) and a column (300 × 7.8 mm) of Bio-Rad Aminex HPX-87H (Hercules, CA, USA) with 5 mM H 2 SO 4 as the mobile phase at a flow rate of 0.5 mL/min, column temperature of 65 °C, and an injection volume at 20 μL as previously described ( Hu et al, 2021 ).…”