Cysteine supplementation enhanced inhibitor tolerance of Zymomonas mobilis for economic lignocellulosic bioethanol production.

Inhibitors in lignocellulosic hydrolysates are toxic to Zymomonas mobilis and reduce its bioethanol production. This study revealed cysteine supplementation enhanced furfural tolerance in Z. mobilis with a 2-fold biomass increase. Transcriptomic study illustrated that cysteine biosynthesis pathway was down-regulated while cysteine catabolism was up-regulated with cysteine supplementation. Mutants for genes involved in cysteine metabolism were constructed, and metabolites in cysteine metabolic pathway including methionine, glutathione, NaHS, glutamate, and pyruvate were supplemented into media. Cysteine supplementation boosted glutathione synthesis or H2S release effectively in Z. mobilis leading to the reduced accumulation of reactive oxygen species (ROS) induced by furfural, while pyruvate and glutamate produced in the H2S generation pathway promoted cell growth by serving as the carbon or nitrogen source. Finally, cysteine supplementation was confirmed to enhance Z. mobilis tolerance against ethanol, acetate, and corncob hydrolysate with an enhanced ethanol productivity from 0.38 to 0.55 g-1∙L-1∙h-1.

Effects of dietary inclusion of Zymomonas mobilis degraded cassava sifting on growth performance, apparent nutrient digestibility, ileal digesta viscosity, and economy of feed conversion of broiler chickens.

A study was carried out to evaluate the effect of dietary inclusion of Zymomonas mobilis degraded cassava sifting (ZDCS) on growth response, apparent nutrient digestibility, and ileal digesta viscosity of broiler chickens. Five diets containing undegraded and degraded cassava sifting were formulated to replace wheat offal at 0, 50, and 100% levels. Two hundred and forty (240) one-day-old Marshall broiler chickens were randomly allotted to the five dietary treatments in a completely randomized design (CRD); significant means were separated using Duncan's multiple range test at p < 0.05. The biodegradation of cassava sifting with Zymomonas mobilis significantly increased crude protein content by 44.59% while crude fiber and neutral detergent fiber significantly decreased by 23.08% and 6.38%, respectively. The results showed that birds fed 50% ZDCS had the best (p > 0.05) feed conversion ratio (FCR) at the starter phase. The replacement of wheat offal with 100% ZDCS improved (p < 0.05) the crude fiber digestibility at both starter and finisher phases. Also, the birds fed 100% ZDCS had the lowest (p < 0.05) value of ileal digesta viscosity. The birds fed 50% ZDCS had the highest (p < 0.05) values of gross revenue, gross profit, rate of return on investment, and economic efficiency while the least values for gross profit, rate of return on investment, and economic efficiency were obtained in 100% ZDCS. The study concluded that replacement of wheat offal with 50% ZDCS in the ration of broiler chickens improved FCR, crude fiber digestibility (CFD), and rate of return on investment and economic efficiency.

Pulque production from fermented agave sap as a dietary supplement in Prehispanic Mesoamerica.

Although in modern societies fermented beverages are associated with socializing, celebration, and ritual, in ancient times they were also importa`nt sources of essential nutrients and potable water. In Mesoamerica, pulque, an alcoholic beverage produced from the fermented sap of several species of maguey plants (Agavaceae; Fig. 1) is hypothesized to have been used as a dietary supplement and risk-buffering food in ancient Teotihuacan (150 B.C. to A.D. 650). Although direct archaeological evidence of pulque production is lacking, organic residue analysis of pottery vessels offers a new avenue of investigation. However, the chemical components of alcoholic beverages are water-soluble, greatly limiting their survival over archaeological timescales compared with hydrophobic lipids widely preserved in food residues. Hence, we apply a novel lipid biomarker approach that considers detection of bacteriohopanoids derived from the ethanol-producing bacterium Zymomonas mobilis for identifying pulque production/consumption in pottery vessels. Gas chromatography-mass spectrometry selected ion monitoring (m/z 191) of lipid extracts of >300 potsherds revealed characteristic bacteriohopanoid distributions in a subset of 14 potsherds. This hopanoid biomarker approach offers a new means of identifying commonly occurring bacterially fermented alcoholic beverages worldwide, including palm wine, beer, cider, perry, and other plant sap- or fruit-derived beverages [Swings J, De Ley J (1977) Bacteriol Rev 41(1):1-46].

Fermentation of reactive-membrane-extracted and ammonium-hydroxide-conditioned dilute-acid-pretreated corn stover.

Acid-pretreated biomass contains various compounds (acetic acid, etc.) that are inhibitory to fermentative microorganisms. Removing or deactivating these compounds using detoxification methods such as overliming or ammonium hydroxide conditioning (AHC) improves sugar-to-ethanol yields. In this study, we treated the liquor fraction of dilute-acid-pretreated corn stover using AHC and a new reactive membrane extraction technique, both separately and in combination, and then the sugars in the treated liquors were fermented to ethanol with the glucose-xylose-fermenting bacterium, Zymomonas mobilis 8b. We performed reactive extraction with mixtures of octanol/Alamine 336 or oleyl alcohol/Alamine 336. The best ethanol yields and rates were achieved for oleyl alcohol-extracted hydrolysates followed by AHC hydrolysates, while octanol-extracted hydrolysates were unfermentable because highly toxic octanol was found in the hydrolysate. Adding olive oil significantly improved yields for octanol-extracted hydrolysate. Additional work is underway to determine if this technology is a cost-effective alternative to traditional hydrolysate conditioning processes.

Production of glucose-fructose oxidoreductase and ethanol by Zymomonas mobilis ATCC 29191 in medium containing corn steep liquor as a source of vitamins.

Different concentrations of corn steep liquor (CSL) were tested in the cultivation of Zymomonas mobilis. Cell growth, ethanol production, and the formation of glucose-fructose oxidoreductase (GFOR) and glucono-delta-lactonase (GL), the enzymes responsible for the bio-production of gluconic acid and sorbitol, were examined. The cell yields using 25 g CSL l(-1) and 40 g CSL l(-1) (Y(X,S) approximately 0.031 g g(-1)) were close to that obtained with 5 g yeast extract (YE) l(-1). With 5 g CSL l(-1) and 15 g CSL l(-1), the nutritional limitation led to smaller Y(X/S). Using 100 g CSL l(-1) produced an inhibitory effect on cell growth. Similar ethanol yields (92-95%) were calculated for each concentration of CSL and also for YE medium. The highest specific GFOR/GL activities (13.2-13.5 U g(-1) dry cell) were reached with 25 g CSL l(-1) and 40 g CSL l(-1), values comparable to that achieved with 5 g YE l(-1). The results confirm that CSL is an effective and cheap supplement for Z. mobilis medium, increasing the economic potential of a large-scale bio-production of sorbitol and gluconic acid by untreated Z. mobilis cells. The economic feasibility of the process is discussed.