Single Batch Fermentation Research Articles

Pilot-scale fermentation of 300 t/a total solvents from sweet sorghum stalk juice

Solvent production from non-grain crops as the substrate via microbial fermentation has been projected to replace highly polluting and unsustainable chemical production methods in fossil oil refinery. Although a promising process pilot-scale studies, the prerequisite for production at industrial scale, are rare. This study reports a complete pilot test process using sweet sorghum stalk juice as feedstock, including the acquisition of sweet sorghum stalk juice, laboratory screening of suitable strains, optimization of industrial conditions, and a pilot-scale test at Yuanxing Bioenergy Co., ltd., China. Strain CIBT S0031 (Clostridium saccharobutylicum DSM13864) performed exceptionally in sweet sorghum stalk juice fermentation compared to other solventogenic clostridia tested. Furthermore, a simple and reliable non-anaerobic inoculation method applicable to extensive industrial solvent fermentation was developed. The optimal minimal medium was adapted for pilot scale fermentation, containing only sweet sorghum stalk juice diluted with industrial water, 1.5 g/L ammonium sulfate, and 1 g/L calcium carbonate. The solvent titers of single batch fermentation (2.36 m3), fed-batch (2.28 m3), and semi-continuous fermentation (7.14 m3) reached 16.5 g/L, 19.29 g/L, and 18.39 g/L, respectively, which replicated the laboratory results at the ton-scale. In the multi-stage process for continuous fermentation (total of 48.3 m3, chained with one breeding tank and three fermenters of 16 m3), 800 kg of solvents was produced with a yield of 0.45 g /g, comparable to corn-based fermentation. This study verified the effectiveness of the tested strain and the pilot process, thus laying a solid foundation for the large-scale production of solvents from a non-grain crop.

Effects of Blending on Phenolic, Colour, Antioxidant and Aroma Components of Cabernet Sauvignon Wine from Xinjiang (China).

High-quality wines in industrial winemaking frequently require a professional winemaker to make adjustments according to the wine of single-batch fermentation. Blending can improve the chemical composition and certain organoleptic properties of wine, promote copigmentation, and increase the complexity of the wine body and aroma. In this study, high-performance liquid chromatography (HPLC) and headspace solid-phase microextraction with gas chromatography coupled to tandem mass spectrometry (HS-SPME-GC-MS/MS) were used to study the effects of adding 20% of Merlot, Marselan, Syrah and Pinot Noir and different blending methods on the nutritional, taste, color and aroma components of Cabernet Sauvignon wine. The results showed that the highest total phenols and flavonoids, the greatest content of antioxidant characteristics, the optimal color according to the parameter of T, red% and blue% and the most abundant aroma were observed both in CGM (grape blending Cabernet Sauvignon and Merlot) and CGS (grape blending Cabernet Sauvignon and Marselan), thus indicating the higher quality and complexity of these wines. In addition, the co-grapes treatment afforded more color and hue value than co-wines, which indicates co-grapes had more stable and more varied colors than co-wines. Our findings provide theoretical support for improving wine quality and craftsmanship.

A possible beneficial effect of Bacteroides on faecal lipopolysaccharide activity and cardiovascular diseases

Faecal lipopolysaccharides (LPS) have attracted attention as potent elements to explain a correlation between the gut microbiota and cardiovascular disease (CVD) progression. However, the underlying mechanism of how specific gut bacteria contribute to faecal LPS levels remains unclear. We retrospectively analysed the data of 92 patients and found that the abundance of the genus Bacteroides was significantly and negatively correlated with faecal LPS levels. The controls showed a higher abundance of Bacteroides than that in the patients with CVD. The endotoxin units of the Bacteroides LPS, as determined by the limulus amoebocyte lysate (LAL) tests, were drastically lower than those of the Escherichia coli LPS; similarly, the Bacteroides LPS induced relatively low levels of pro-inflammatory cytokine production and did not induce sepsis in mice. Fermenting patient faecal samples in a single-batch fermentation system with Bacteroides probiotics led to a significant increase in the Bacteroides abundance, suggesting that the human gut microbiota could be manipulated toward decreasing the faecal LPS levels. In the clinical perspective, Bacteroides decrease faecal LPS levels because of their reduced LAL activity; therefore, increasing Bacteroides abundance might serve as a novel therapeutic approach to prevent CVD via reducing faecal LPS levels and suppressing immune responses.

Potential of hydrogen production from sugarcane juice by Ethanoligenens harbinense Yuan-3

Inexpensive biomass is an ideal substrate for low-cost production of biohydrogen, but little was known about the biomass utilization performance of the ethanol-type hydrogen-producing bacteria Ethanoligenens harbinense. This study investigated the feasibility and performance of biohydrogen production by Ethanoligenens harbinense from sugarcane juice (SJ). Medium and process were firstly optimized with SJ as carbon source and the highest hydrogen yield was obtained when SJ was hydrolyzed by acid, and the medium contained 10 g/L sugar and 3 g/L yeast extract with pH at 6.0. Compared to batch fermentation, fed-batch fermentation with cell recycle showed significant improvement in hydrogen productivity and yield. The maximum productivity reached 5.22 mmol-H2/L•h, 201.7% higher than that of the single batch (1.73 mmol-H2/L•h). The highest H2 yield was 2.23 mol-H2/mol-hexose, 65.2% higher than that of single batch fermentation. Cell immobilization with the fibrous bed bioreactor (FBB) also improved hydrogen productivity to 2.6 times that of batch fermentation with free cells. This study demonstrated the feasibility of hydrogen production from SJ with Ethanoligens sp., and a great improvement in hydrogen production was obtained by recycling cells and immobilizing cells in a fibrous bed bioreactor.

Effect of Resistant Starch on the Gut Microbiota and Its Metabolites in Patients with Coronary Artery Disease.

Aim: Bacteroides vulgatus and B. dorei have a protective effect against atherosclerosis, suggesting that expansion of these species in the gut microbiota could help patients with coronary artery disease (CAD). This study aimed to investigate the effect of resistant starch (RS) on the gut microbiota and its metabolites in fecal sample cultures from patients with CAD and individuals without CAD, using a single-batch fermentation system.Methods: Fecal samples from 11 patients with CAD and 10 individuals without CAD were fermented for 30 h with or without RS in the Kobe University Human Intestinal Microbiota Model (KUHIMM). Gut microbiota and the abundance of B. vulgatus and B. dorei were analyzed using 16S ribosomal ribonucleic acid (rRNA) gene sequencing and the quantitative polymerase chain reaction. Short-chain fatty acids were analyzed using high-performance liquid chromatography.Results: Gut microbial analysis showed significantly lower levels of B. vulgatus and B. dorei in the original fecal samples from patients with CAD, which was simulated after 30 h of fermentation in the KUHIMM. Although RS significantly increased the absolute numbers of B. vulgatus and B. dorei, and butyrate levels in CAD fecal sample cultures, the numbers varied among each patient.Conclusions: The effect of RS on gut microbiota and its metabolites in the KUHIMM varied between CAD and non-CAD fecal sample cultures. The KUHIMM may be useful for preclinical evaluations of the effects of RS on the gut microbiota and its metabolites.

Exploring cellular fatty acid composition and intracellular metabolites of osmotic-tolerant mutant Lactobacillus paracasei NCBIO-M2 for highly efficient lactic acid production with high initial glucose concentration

High titer, productivity and yield are the main pre-requisites of an efficient lactic acid production process. However, the hyperosmotic stress inhibits cell metabolism in the later phase of fermentation. In this study, an osmotic-tolerant mutant named Lactobacillus paracasei NCBIO01-M2 was obtained through a high-throughput screening technology, which exhibited a higher tolerance to osmotic stress due to its more flexible regulation of the unsaturated fatty acid proportion along with the intracellular compatible solute pools. The mutant successfully consumed all 248 g/L initial glucose and produced 223.7 g/L lactic acid with a productivity of 5.53 g/L/h in a single batch fermentation by the neutralizing agent strategy. Moreover, similar fermentation performances were also achieved in the open fermentation mode without sterilization by the mutant, which suggested that the mutant would be a potential for cost-effective commercial lactic acid production.

Reconstruction of metabolic module with improved promoter strength increases the productivity of 2-phenylethanol in Saccharomyces cerevisiae

Background2-phenylethanol (2-PE) is an important aromatic compound with a lovely rose-like scent. Saccharomyces cerevisiae is a desirable microbe for 2-PE production but its natural yield is not high, and one or two crucial genes’ over-expression in S. cerevisiae did not improve 2-PE greatly.ResultsA new metabolic module was established here, in which, permease Gap1p for l-phenylalanine transportation, catalytic enzymes Aro8p, Aro10p and Adh2p in Ehrlich pathway respectively responsible for transamination, decarboxylation and reduction were assembled, besides, glutamate dehydrogenase Gdh2p was harbored for re-supplying another substrate 2-oxoglutarate, relieving product glutamate repression and regenerating cofactor NADH. Due to different promoter strengths, GAP1, ARO8, ARO9, ARO10, ADH2 and GDH2 in the new modularized YS58(G1-A8-A10-A2)-GDH strain enhanced 11.6-, 15.4-, 3.6-, 17.7-, 12.4- and 7.5-folds respectively, and crucial enzyme activities of aromatic aminotransferases and phenylpyruvate decarboxylase were 4.8- and 7-folds respectively higher than that of the control.ConclusionsUnder the optimum medium and cell density, YS58(G1-A8-A10-A2)-GDH presented efficient 2-PE synthesis ability with ~ 6.3 g L−1 of 2-PE titer in 5-L fermenter reaching 95% of conversation ratio. Under fed-batch fermentation, 2-PE productivity at 24 h increased 29% than that of single-batch fermentation. Metabolic modularization with promoter strategy provides a new prospective for efficient 2-PE production.

Improved production of isobutanol in pervaporation-coupled bioreactor using sugarcane bagasse hydrolysate in engineered Enterobacter aerogenes

A process of isobutanol production from sugarcane bagasse hydrolysates in Enterobacter aerogenes was developed here with a pervaporation-integrated procedure. Isobutanol pathway was overexpressed in a mutant strain with eliminated byproduct-forming enzymes (LdhA, BudA, and PflB). A glucose-and-xylose–coconsuming ptsG mutant was constructed for effective utilization of lignocellulosic biomass. Toxic effects of isobutanol were alleviated by in situ recovery via a pervaporation procedure. Compared to single-batch fermentation, cell growth and isobutanol titer were improved by 60% and 100%, respectively, in the pervaporation-integrated fermentation process. A lab-made cross-linked polydimethylsiloxane membrane was cast on polyvinylidene fluoride and used in the pervaporation process. The membrane-penetrating condensate contained 55–226 g m−2 h−1 isobutanol with 6–25 g L−1 ethanol after separation. This study offers improved fermentative production of isobutanol from lignocellulosic biomass with a pervaporation procedure.

Taurine does not affect the composition, diversity, or metabolism of human colonic microbiota simulated in a single-batch fermentation system.

Accumulating evidence suggests that dietary taurine (2-aminoethanesulfonic acid) exerts beneficial anti-inflammatory effects in the large intestine. In this study, we investigated the possible impact of taurine on human colonic microbiota using our single-batch fermentation system (Kobe University Human Intestinal Microbiota Model; KUHIMM). Fecal samples from eight humans were individually cultivated with and without taurine in the KUHIMM. The results showed that taurine remained largely undegraded after 30 h of culturing in the absence of oxygen, although some 83% of the taurine was degraded after 30 h of culturing under aerobic conditions. Diversity in bacterial species in the cultures was analyzed by 16S rRNA gene sequencing, revealing that taurine caused no significant change in the diversity of the microbiota; both operational taxonomic unit and Shannon-Wiener index of the cultures were comparable to those of the respective source fecal samples. In addition, principal coordinate analysis indicated that taurine did not alter the composition of bacterial species, since the 16S rRNA gene profile of bacterial species in the original fecal sample was maintained in each of the cultures with and without taurine. Furthermore, metabolomic analysis revealed that taurine did not affect the composition of short-chain fatty acids produced in the cultures. These results, under these controlled but artificial conditions, suggested that the beneficial anti-inflammatory effects of dietary taurine in the large intestine are independent of the intestinal microbiota. We infer that dietary taurine may act directly in the large intestine to exert anti-inflammatory effects.

A Single-Batch Fermentation System to Simulate Human Colonic Microbiota for High-Throughput Evaluation of Prebiotics.

We devised a single-batch fermentation system to simulate human colonic microbiota from fecal samples, enabling the complex mixture of microorganisms to achieve densities of up to 1011 cells/mL in 24 h. 16S rRNA gene sequence analysis of bacteria grown in the system revealed that representatives of the major phyla, including Bacteroidetes, Firmicutes, and Actinobacteria, as well as overall species diversity, were consistent with those of the original feces. On the earlier stages of fermentation (up to 9 h), trace mixtures of acetate, lactate, and succinate were detectable; on the later stages (after 24 h), larger amounts of acetate accumulated along with some of propionate and butyrate. These patterns were similar to those observed in the original feces. Thus, this system could serve as a simple model to simulate the diversity as well as the metabolism of human colonic microbiota. Supplementation of the system with several prebiotic oligosaccharides (including fructo-, galacto-, isomalto-, and xylo-oligosaccharides; lactulose; and lactosucrose) resulted in an increased population in genus Bifidobacterium, concomitant with significant increases in acetate production. The results suggested that this fermentation system may be useful for in vitro, pre-clinical evaluation of the effects of prebiotics prior to testing in humans.

Improved conversion of rice straw to ethanol and xylitol by combination of moderate temperature ammonia pretreatment and sequential fermentation using Candida tropicalis

Rice straw is a promising feedstock for sustained production of ethanol and value-added products. In this study, production of ethanol with xylitol from rice straw was improved by employing moderate aqueous ammonia pretreatment and sequential fermentation. The pretreatment removed significant amount of lignin and enhanced the enzymatic digestibility of rice straw by four fold. The analysis of the pretreated rice straw by SEM, XRD and FTIR showed significant changes in physicochemical structure, favoring enzymatic hydrolysis. The fermentability of the sugar hydrolyzate to ethanol was evaluated in repeated batch fermentation with cell recycling. Ethanol yield of 98% was achieved up to three batches of recycling of cells of Candida tropicalis. Fermentation of glucose and xylose in the hydrolyzate to ethanol and xylitol was studied using C. tropicalis in single and two-stage sequential fermentations. While ethanol yield was same, xylitol yield was higher in the two-stage fermentation than single batch fermentation. The results suggest that the sequential fermentation of sugar hydrolyzate of ammonia pretreated rice straw would be a promising process for production of ethanol and xylitol.

Dried Spent Yeast and Its Hydrolysate as Nitrogen Supplements for Single Batch and Repeated-Batch Ethanol Fermentation from Sweet Sorghum Juice

Dried spent yeast (DSY) and its hydrolysate (DSYH) were used as low-cost nitrogen supplements to improve ethanol production from sweet sorghum juice by Saccharomyces cerevisiae NP01 under very high gravity (VHG) fermentation (280 g·L−1 of total sugar) conditions. The supplemented DSY and DSYH concentrations were 11, 16 and 21 g·L−1, corresponding to a yeast extract nitrogen content of 6, 9 and 12 g·L−1, respectively. The initial yeast cell concentration for ethanol fermentation was approximately 5 × 107 cells·mL−1. The fermentation was carried out in single batch mode at 30 °C in 1-L air-locked bottles with an agitation rate of 100 rpm. Ethanol production from the juice with and without yeast extract (9 g·L−1) was also performed as control treatments. The results showed that DSY at 21 g·L−1gave the highest ethanol concentration (PE, 107 g·L−1) and yield (Yp/s, 0.47 g·g−1). The use of DSYH at the same DSY concentration improved ethanol productivity (Qp), but not PE and Yp/s. The ethanol production efficiencies of the juice under DSY and DSYH supplementations were markedly higher than those without nutrient supplementation. However, the PE and Qp values of the juice containing 21 g·L−1 of DSY was approximately 7 g·L−1 and 0.62 g·L−1·h−1 lower than those under the presence of yeast extract (9 g·L−1), respectively. At the end of the single batch fermentation under the optimum DSY concentration, the sugar consumption was approximately 80%. Therefore in the repeated-batch fermentation, the initial total sugar was reduced to 240 g·L−1. The results showed that the system could be carried out at least 20 successive batches with the average PE, Yp/s and Qp of 95 g·L−1, 0.46 g·g−1 and 1.45 g·L−1·h−1, respectively.

Improved n-butanol production by solvent tolerant Clostridium beijerinckii

Abstract n-butanol fermentation by Clostridium beijerinckii ATCC 10132 was investigated by optimization of various physiological and nutritional parameters. Nitrogen source and metal ions played a crucial role on the titre of n-butanol produced in the fermentation. Optimization of the parameters resulted in about 6-fold increase and an unprecedented titre of 20 g L−1 of n-butanol in 72 h incubation period. The process could be scaled up to 3 L level with similar titres. The strain was found to be tolerant to 25 g L−1 n-butanol under optimized conditions and the tolerance could also be demonstrated by the strain’s ability to accumulate rhodamine 6 G. Adaptation of the strain to increased solvent in the medium was accompanied by increased expression of the chaperone, GroEL and change in fatty acid profile of total lipids. This is the first report wherein high titre of n-butanol has been obtained in single batch fermentation without resorting to solvent stripping or strain improvement.

Oxygen Kinetic and Metabolic Parameters for the YeastTrigonopsis variabilis

The metabolic and kinetic parameters of oxygen consumption by the yeast Trigonopsis variabilis under conditions of induced and non-induced D-amino acid oxidase are described for the first time. These parameters can be calculated from the results of a single batch fermentation running at an oxygen-limiting condition. The values obtained for the parameters may be used as a basis for the calculation of the aeration and stirring requirements and optimal oxygen conditions for the growth of T. variabilis in batch, fed-batch or continuous fermentations.

The production of ethanol from sucrose using Zymomonas mobilis

A new single-batch fermentation process for the commercial production of ethanol from refined sucrose, raw sugar, sugar cane juice and sugar cane syrup has been developed using a highly adapted and efficient strain of Zymomonas mobilis. The process gives a 94–98% sucrose hydrolysis efficiency and a 95–98% ethanol conversion efficiency. Within 24–30 h, 200 g/l sucrose is converted to produce 95.5 g/l ethanol. Reinoculation is carried out from the fermented broth without the need for centrifugation or membrane filtration.