Polyhydroxyalkanoates (PHAs) have obtained much attention in biomaterial fields due to their similar physicochemical properties to those of the petroleum-derived plastics. Poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)] is one member of the PHAs family, and has better toughness and transparency compared to existing polylactic acid (PLA) and poly[(R)-3-hydroxybutyrate] [P(3HB)]. First, we confirmed the one-step biosynthesis of P(LA-co-3HB) with the lactate fraction of 23.8 mol% by introducing P(3HB-co-LA) production module into Escherichia coli MG1655. Then, the lactate fraction was increased to 37.2 mol% in the dld deficient strain WXJ01-03. The genes encoding the thioesterases, ydiI and yciA, were further knocked out, and the lactate fraction in the P(3HB-co-LA) was improved to 42.3 mol% and 41.1 mol% respectively. Strain WXJ03-03 with dld, ydiI and yciA deficient was used for the production of the LA-enriched polymer, and the lactate fraction was improved to 46.1 mol%. Notably, the lactate fraction in P(3HB-co-LA) from xylose was remarkably higher than from glucose, indicating xylose as a potent carbon source for P(3HB-co-LA) production. Therefore, the deficiency of thioesterase may be considered as an effective strategy to improve the lactate fraction in P(3HB-co-LA) in xylose fermentation.
Escherichia coli/genetics* ; Hydroxybutyrates ; Lactic Acid ; Polyesters ; Polyhydroxyalkanoates ; Xylose

Effective utilization of xylose is a basis for economic production of biofuels or chemicals from lignocellulose biomass. Over the past 30 years, through metabolic engineering, evolutionary engineering and other strategies, the metabolic capacity of xylose of the traditional ethanol-producing microorganism Saccharomyces cerevisiae has been significantly improved. In recent years, the reported results showed that the transcriptome and metabolome profiles between xylose and glucose metabolism existed significant difference in recombinant yeast strains. Compared with glucose, the overall process of xylose metabolism exhibits Crabtree-negative characteristics, including the limited glycolytic pathway activity, which reduces the metabolic flux of pyruvate to ethanol, and the enhanced cytosolic acetyl-CoA synthesis and respiratory energy metabolism. These traits are helpful to achieve efficient synthesis of downstream products using pyruvate or acetyl-CoA as precursors. This review provides a detailed overview on the modification and optimization of xylose metabolic pathways in S. cerevisiae, the characteristics of xylose metabolism, and the construction of cell factories for production of chemicals using xylose as a carbon source. Meanwhile, the existed difficulties and challenges, and future studies on biosynthesis of bulk chemicals using xylose as an important carbon source are proposed.
Biofuels ; Ethanol ; Fermentation ; Metabolic Engineering ; Saccharomyces cerevisiae/genetics* ; Xylose

BACKGROUND: The performance of the self-monitoring of blood glucose in patients with diabetes should be properly evaluated to ensure strict glycemic control. This study evaluated the self-testing Blood Glucose Monitoring System GlucoDr.S™ (All Medicus Co., Ltd., Korea). METHODS: This study recruited 120 patients. Use of the glucometer was evaluated according to ISO 15197:2013 guidelines. The YSI 2300 STAT PLUS Glucose Analyzer (YSI Life Sciences, USA) was used as the reference device. RESULTS: The standard deviation and coefficients of variation ranges for measurement repeatability and intermediate measurement precision conducted with 10 meters and 3 reagent lots on the same day were 2.7–3.2 mg/dL (<100 mg/dL) and 3.4–3.7% (≥100 mg/dL), respectively, and 3.7 mg/dL (<100 mg/dL) and 2.1–2.6% (≥100 mg/dL), respectively. Each coefficient of determination (R2) for linearity of the 3 reagent lots was >0.99. The influence effect of hematocrit and the 24 interference agents was not significant, except for xylose. A system accuracy test was conducted with 100 subjects taking duplicate measurements from each of the 3 reagent lots. When glucose levels were <100 mg/dL and ≥100 mg/dL, >95% of the samples were within ±15 mg/dL and within ±15% of the average measured values of the reference measurement, respectively. In Consensus Error grid analysis, all results were distributed in zone A and B. The results of the user performance evaluation using 115 lay persons were also included in the acceptance range. CONCLUSION: The GlucoDr.S™ showed acceptable performance according to the ISO 15197:2013 guidelines and could be a clinically useful self-testing glucometer.
Biological Science Disciplines ; Blood Glucose* ; Consensus ; Glucose ; Hematocrit ; Humans ; Xylose

Plackett-Burman (PB) design and central composite design (CCD) were applied to optimize of xylose fermentation for ethanol production by Candida shehatae HDYXHT-01. The PB results showed that (NH4)2SO4, KH2PO4, yeast extract and inoculum volume were the main affecting factors. With ethanol productivity as the target response, the optimal fermentation was determined by CCD and response surface analysis (RSM). The optimal fermentation conditions were (NH4)2SO4 1.73 g/L, KH2PO4 3.56 g/L, yeast extract 2.62 g/L and inoculum volume 5.66%. Other fermentation conditions were xylose 80 g/L, MgSO47H20 0.1 g/L, pH 5.0 and 250 mL flask containing 100 mL medium and cultivated at 30 degrees C for 48 h and the agitation speed was 140 r/min. Under this fermentation conditions, ethanol productivity was 26.18 g/L, which was 1.15 times of the initial.
Candida ; metabolism ; Ethanol ; metabolism ; Fermentation ; Industrial Microbiology ; Xylose ; metabolism

It is of great significance to use biosynthesis to transform the inorganic substance formaldehyde into organic sugars. Most important in this process was to find a suitable catalyst combination to achieve the dimerization of formaldehyde. In a recent report, an engineered glycolaldehyde synthase was reported to catalyze this reaction. It could be combined with engineered D-fructose-6-phosphate aldolase, a "one-pot enzyme" method, to synthesize L-xylose using formaldehyde and the conversion rate could reach up to 64%. This process also provides a reference for the synthesis of other sugars. With the increasing consumption of non-renewable resources, it was of great significance to convert formaldehyde into sugar by biosynthesis.
Biocatalysis ; Formaldehyde ; chemistry ; Fructose-Bisphosphate Aldolase ; metabolism ; Xylose ; chemical synthesis

INTRODUCTION: Small intestinal bacterial overgrowth (SIBO) occurs in varying frequency in irritable bowel syndrome (IBS). We studied the frequency of SIBO in IBS and chronic non-specific diarrhea (CNSD). METHODS: 129 patients with IBS (Manning's criteria), 73 with CNSD (> or = 4 weeks diarrhea with two of these tests normal [urine D-xylose, fecal fat and duodenal biopsy]) and 51 healthy controls (HC) were evaluated for SIBO using glucose hydrogen breath test (GHBT). Diarrhea-predominant IBS (D-IBS) was grouped into CNSD. Rise in breath hydrogen 12 ppm above basal following 100 g glucose was diagnostic of SIBO. RESULTS: Of 129 patients with IBS, 7 were constipation (C-IBS), and 122 were of indeterminate type (I-IBS). Patients with IBS were younger than HC and CNSD (IBS vs. HC: 36.6 yr +/- 11.4 vs. 44.1 yr +/- 13.6, p = 0.001; IBS vs. CNSD: 36.6 yr +/- 11.4 vs. 42 yr +/- 14.5, p = 0.003). Patients with CNSD were comparable to HC in age (42 yr +/- 14.5 vs. 44.1 yr +/- 13.6, p = ns). Patients with IBS were more often male than HC [108/129 (83.7%) vs. 34/51 (66.7%) p = 0.02]; gender of CNSD and HC was comparable [male 39/73 (53.4%) vs. 34/51 (66.7%) p = ns]. SIBO was commoner in CNSD than HC [16 (21.9%) vs. 1 (2%), p = 0.003], but was comparable in IBS and HC [11 (8.5%) vs. 1 (2%), p = 0.18]. Patients with CNSD more often had SIBO than IBS [16 (21.9%) vs. 11 (8.5%), p = 0.007]. CONCLUSIONS: SIBO was more common in CNSD including D-IBS than other types of IBS and HC.
Breath Tests ; Constipation ; Diarrhea ; Glucose ; Humans ; Hydrogen ; Irritable Bowel Syndrome ; Malabsorption Syndromes ; Male ; Xylose

To realize the simultaneous fermentation of xylose and glucose, ptsG (one of the glucose-PTS genes) was deleted from the engineered ethanologenic Escherichia coli SZ470 (deltapflB, deltafrdABCD, deltaackA, deltaldhA), resulting in loss of glucose effect in the mutant SZ470P (deltaptsG). When tested in 5% mixture of glucose (2.5%) and xylose (2.5%), SZ470P simultaneously used glucose (13 g/L) and xylose (20 g/L) whereas the parent strain SZ470 sequentially used glucose (25 g/L) then xylose (5 g/L). Upon completion of the fermentation, both strains achieved similar product yield of 89%. SZ470P produced 15.01 g/L of ethanol, which was 14.32% higher than that produced by SZ470 (12.86 g/L). Deleting ptsG gene enabled the mutant strain SZ470P to simultaneously use both glucose and xylose and achieve better ethanol production.
Escherichia coli ; enzymology ; genetics ; Ethanol ; chemistry ; Fermentation ; Glucose ; chemistry ; Phosphoenolpyruvate Sugar Phosphotransferase System ; genetics ; Xylose ; chemistry

Chromosomal integration enables stable phenotype and therefore has become an important strategy for breeding of industrial Saccharomyces cerevisiae strains. pAUR135 is a plasmid that enables recycling use of antibiotic selection marker, and once attached with designated homologous sequences, integration vector for stable expression can be constructed. Development of S. cerevisiae strains by metabolic engineering normally demands overexpression of multiple genes, and employing pAUR135 plasmid, it is possible to construct S. cerevisiae strains by combinational integration of multiple genes in multiple sites, which results in different ratios of expressions of these genes. Xylose utilization pathway was taken as an example, with three pAUR135-based plasmids carrying three xylose assimilation genes constructed in this study. The three genes were sequentially integrated on the chromosome of S. cerevisiae by combinational integration. Xylose utilization rate was improved 24.4%-35.5% in the combinational integration strain comparing with that of the control strain with all the three genes integrated in one location. Strain improvement achieved by combinational integration is a novel method to manipulate multiple genes for genetic engineering of S. cerevisiae, and the recombinant strains are free of foreign sequences and selection markers. In addition, stable phenotype can be maintained, which is important for breeding of industrial strains. Therefore, combinational integration employing pAUR135 is a novel method for metabolic engineering of industrial S. cerevisiae strains.
Genetic Engineering ; methods ; Genetic Vectors ; Metabolic Engineering ; Plasmids ; genetics ; Saccharomyces cerevisiae ; genetics ; Xylose ; metabolism

Pathway engineering was the third generation of gene engineering. Its main goals were to change metabolic flux and open a new metabolic pathway in organism. Application of recombinant DNA methods to restructure metabolic networks can improve production of metabolite and protein products by altering pathway distributions and rates. Ethanol is the most advanced liquid fuel because it is environmentally friendly. Enhancing fuel ethanol production will require developing lower-cost feedstock, and only lignocellulosic feedstock is available in sufficient quantities to substitute for corn starch. Xylose is the major pentose found in lignocellulosic materials and after glucose the most abundant sugar available in nature. Recently a lot of attentions have been focused on designing metabolic pathway of Saccharomyces cerevisiae in order to expand the substrate of ethanol fermentation, because it is a traditional ethanol producing strain and has wonderful properties for ethanol industry. However, it can not utilize xylose but convert the isomer, xylulose. Many attempts are based on introducing the genes in the pathway of xylose metabolism. The further research includes overexpressing the key enzyme or decreasing the unimportant flux. The sugars in lignocellulose hydrolyzates, therefore, could be efficiently utilized. Here, we describe the ethanol pathway engineering progress in ethanol fermentation from xylose with recombinant Saccharomyces cerevisiae.
Biotechnology ; methods ; Ethanol ; metabolism ; Fermentation ; genetics ; physiology ; Recombination, Genetic ; genetics ; Saccharomyces cerevisiae ; genetics ; metabolism ; Xylose ; metabolism

Co-fermentation of glucose and xylose is critical for cellulosic ethanol, as xylose is the second most abundant sugar in lignocellulosic hydrolysate. In this study, a xylose-utilizing recombinant Zymomonas mobilis TSH01 was constructed by gene cloning, and ethanol fermentation of the recombinant was evaluated under batch fermentation conditions with a fermentation time of 72 h. When the medium containing 8% glucose or xylose, was tested, all glucose and 98.9% xylose were consumed, with 87.8% and 78.3% ethanol yield, respectively. Furthermore, the medium containing glucose and xylose, each at a concentration of 8%, was tested, and 98.5% and 97.4% of glucose and xylose was fermented, with an ethanol yield of 94.9%. As for the hydrolysate of corn stover containing 3.2% glucose and 3.5% xylose, all glucose and 92.3% xylose were consumed, with an ethanol yield of 91.5%. In addition, monopotassium phosphate can facilitate the consumption of xylose and enhance ethanol yield.
Ethanol ; metabolism ; Fermentation ; Glucose ; metabolism ; Recombination, Genetic ; Xylose ; metabolism ; Zymomonas ; genetics ; metabolism