Engineered Cell Elongation Promotes Extracellular Electron Transfer of Shewanella Oneidensis.

To investigate how cell elongation impacts extracellular electron transfer (EET) of electroactive microorganisms (EAMs), the division of model EAM Shewanella oneidensis (S. oneidensis) MR-1 is engineered by reducing the formation of cell divisome. Specially, by blocking the translation of division proteins via anti-sense RNAs or expressing division inhibitors, the cellular length and output power density are all increased. Electrophysiological and transcriptomic results synergistically reveal that the programmed cell elongation reinforces EET by enhancing NADH oxidation, inner-membrane quinone pool, and abundance of c-type cytochromes. Moreover, cell elongation enhances hydrophobicity due to decreased cell-surface polysaccharide, thus facilitates the initial surface adhesion stage during biofilm formation. The output current and power density all increase in positive correction with cellular length. However, inhibition of cell division reduces cell growth, which is then restored by quorum sensing-based dynamic regulation of cell growth and elongation phases. The QS-regulated elongated strain thus enables a cell length of 143.6 ± 40.3 µm (72.6-fold of that of S. oneidensis MR-1), which results in an output power density of 248.0 ± 10.6 mW m-2 (3.41-fold of that of S. oneidensis MR-1) and exhibits superior potential for pollutant treatment. Engineering cellular length paves an innovate avenue for enhancing the EET of EAMs.

Impact of a random TN5 mutation on endoglucanase secretion in ruminal cellulolytic Escherichia coli.

OBJECTIVE: Most protein secretion systems are found in gram-negative bacteria, but the mechanism of endoglucanase (BcsZ) secretion in Escherichia coli (E. coli) remains unclear. METHODS: In this study, we used JBZ-DH5α (which overexpresses BcsZ on the E. coli DH5α genome) as the initial strain. A mutant library was created by randomly inserting the TN5 transposon into the genome, and mutants with reduced transparent circles were identified on Congo red plates. The insertion sites of transposons in the genome were determined through whole-genome sequencing. RESULTS: The results revealed that the genes rnc, lon, and suhB, which encode RNC-ribonuclease III (RNC), LON-protease (LON), and SuhB-inositol phosphatase (SuhB), respectively, were disrupted. BcsZ secretion decreased in E. coli DH5α when the lon, rnc, or suhB genes were deleted, but the overexpression of these genes restored their secretion levels. CONCLUSION: These findings suggest that the lon, rnc, and suhB genes play a role in BcsZ secretion in E. coli, potentially enhancing our knowledge of BcsZ secretion and offering a strategy to increase protein secretion in E. coli as a cell factory.

Engineering Shewanella oneidensis-Carbon Felt Biohybrid Electrode Decorated with Bacterial Cellulose Aerogel-Electropolymerized Anthraquinone to Boost Energy and Chemicals Production.

Interfacial electron transfer between electroactive microorganisms (EAMs) and electrodes underlies a wide range of bio-electrochemical systems with diverse applications. However, the electron transfer rate at the biotic-electrode interface remains low due to high transmembrane and cell-electrode interfacial electron transfer resistance. Herein, a modular engineering strategy is adopted to construct a Shewanella oneidensis-carbon felt biohybrid electrode decorated with bacterial cellulose aerogel-electropolymerized anthraquinone to boost cell-electrode interfacial electron transfer. First, a heterologous riboflavin synthesis and secretion pathway is constructed to increase flavin-mediated transmembrane electron transfer. Second, outer membrane c-Cyts OmcF is screened and optimized via protein engineering strategy to accelerate contacted-based transmembrane electron transfer. Third, a S. oneidensis-carbon felt biohybrid electrode decorated with bacterial cellulose aerogel and electropolymerized anthraquinone is constructed to boost the interfacial electron transfer. As a result, the internal resistance decreased to 42 Ω, 480.8-fold lower than that of the wild-type (WT) S. oneidensis MR-1. The maximum power density reached 4286.6 ± 202.1 mW m-2, 72.8-fold higher than that of WT. Lastly, the engineered biohybrid electrode exhibited superior abilities for bioelectricity harvest, Cr6+ reduction, and CO2 reduction. This study showed that enhancing transmembrane and cell-electrode interfacial electron transfer is a promising way to increase the extracellular electron transfer of EAMs.

Analysis of the improved mechanism of Rhodobacter sphaeroides VK-2-3 coenzyme Q10 by reverse metabolic engineering.

Coenzyme Q10 (CoQ10) is an essential medicinal ingredient. In this study, we obtained a high-yielding mutant strain of CoQ10, VK-2-3, by subjecting R. sphaeroides V-0 (V-0) to a 12C6+ heavy ion beam and high-voltage prick electric field treatment. To investigate the mutation mechanism, the complete genomes of VK-2-3 and V-0 were sequenced. Collinearity analysis revealed that the nicotinamide adenine dinucleotide-dependent dehydrogenase (NAD) gene underwent rearrangement in the VK-2-3 genome. The NAD gene was overexpressed and silenced in V-0, and this construct was named RS.NAD and RS.ΔNAD. The results showed that the titers of CoQ10 in the RS.NAD and RS.ΔNAD increased and decreased by 16.00 and 33.92%, respectively, compared to those in V-0, and these differences were significant. Our results revealed the mechanism by which the VK-2-3 CoQ10 yield increases through reverse metabolic engineering, providing insights for genetic breeding and mechanistic analysis.

[Retracted] MicroRNA­148a suppresses epithelial­mesenchymal transition and invasion of pancreatic cancer cells by targeting Wnt10b and inhibiting the Wnt/ß­catenin signaling pathway.

Following the publication of this article, a concerned reader drew to the Editor's attention that various of the data panels showing the results from Transwell cell migration and invasion assay experiments in Figs. 2D and 4D contained groupings of cells that were markedly similar, even though the cells appeared in separate panels that were intended to show the results from different experiments. In addition, the cell images shown in Fig. 2B were strikingly similar to data that had appeared in different form in another article published by different authors at a different research institution. After having conducted an internal investigation of this matter, the Editor of Oncology Reports has judged that the groupings of cells, appearing as they did among various different panels in Figs. 2 and 4, were too extensive that their apperance could have been attributed to pure coincidence. Also in view of the fact that some of the data were derived from a previously published source, the Editor has decided that this article should be retracted from the publication. After having been in contact with the authors of this study, they agreed with the Editor's decision to retract this article. The Editor sincerely apologizes to the readership for any incovenience caused, and we thank the reader for bringing this matter to our attention. [Oncology Reports 38: 301­308, 2017; DOI: 10.3892/or.2017.5705].

Isolation and Screening of High-Yielding α-Amylase Mutants of Bacillus subtilis by Heavy Ion Mutagenesis.

To improve fermentative production of α-amylase, heavy-ion mutagenesis technology was used to irradiate Bacillus subtilis (B. subtilis) to obtain the high yielding mutants in this study. After continuous cultivation for 12 generations, eight mutants exhibited positive mutation rate with greater H/C. The α-amylase production was stable and obviously exceeded that by the parent strain, which shows that the mutants have a good genetic stability. Among the mutants, the α-amylase activity of B. subtilis KC-180-2 was 72.26 U·mL-1, which was 82.34% higher than that of the original strain. After optimization of fermentation conditions and media, the α-amylase activity of B. subtilis KC-180-2 reached a maximum of 156.83 U·mL-1 at 36 h in a bioreactor. In addition, the optimized fermentation temperature of B. subtilis KC-180-2 was increased to 49℃, indicating B. subtilis KC-180-2 possesses high-temperature resistance, which has great application prospects for industrial fermentation for α-amylase production.

Overexpression of enzymes in glycolysis and energy metabolic pathways to enhance coenzyme Q10 production in Rhodobacter sphaeroides VK-2-3.

We subjected the components of the glycolysis and energy metabolism pathways of Rhodobacter sphaeroides (R. sphaeroides) to metabolic engineering to improve the titer and yield of coenzyme Q10 (CoQ10). Phosphofructokinase (PFK), cyclic adenylate-dependent protein kinase (PKAC), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and adenosine triphosphate hydrolase (KdpC) were overexpressed in R. sphaeroides VK-2-3 (VK-2-3). The strains were labeled R. sphaeroides PFK (RS.PFK), RS.PKAC, RS.PFK-PKAC, RS.KdpC, RS.GAPDH, and RS.KdpC-GAPDH. Results showed that the CoQ10 titers of RS.PFK, RS.PKAC, and RS.PFK-PKAC were 300.96 ± 0.87, 405.94 ± 4.77, and 379.94 ± 0.42 mg/l, respectively. The CoQ10 titers of RS.PFK and VK-2-3 were not significantly different; however, those for RS.PKAC and RS.PFK-PKAC were 13 and 6% higher than that of VK-2-3, respectively. Further, the titers of RS.KdpC, RS.GAPDH, and RS.KdpC-GAPDH were 360.17 ± 0.39, 409.79 ± 0.76, and 359.87 ± 1.14 mg/l, respectively. The titers of RS.KdpC and RS.KdpC-GAPDH were not significantly different from that for VK-2-3, whereas that for RS.GAPDH was 14% higher than that of VK-2-3. Finally, when the cultures of RS.GAPDH and VK-2-3 were scaled up in 5-L fermenters, the CoQ10 titers and RS.GAPDH yields increased by 44.3 and 37.8%, respectively, compared with VK-2-3.To the best of our knowledge, the glycolysis pathway of R. sphaeroides was studied for the first time in this study. We genetically modified the components of the energy metabolism pathway to obtain the strain with high yield of CoQ10 mutant RS.GAPDH. The findings of this study can serve as a basis for future studies involving metabolic engineering of CoQ10-producing strains.

Systematic Analysis of Escherichia coli Isolates from Sheep and Cattle Suggests Adaption to the Rumen Niche.

The commonly used laboratory bacterium Escherichia coli normally does not produce and secrete cellulases due to its complex bilayer membrane structure and poor secretory apparatus. In our previous study, the cellulolytic E. coli strain ZH-4 with extracellular cellulase activity was found in the bovine rumen. In this study, we demonstrate that the secretion of cellulase is a common feature of E. coli isolates from the rumen of animals such as sheep and cattle. Physiological phenotype characterization of these E. coli isolates, together with genome, transcriptome, and comparative genomics analysis, suggests their adaption to the rumen niche. The higher growth rate of the isolated strains under aerobic conditions meets the competitive requirements of the strains in rumen microecosystem, while anaerobic accumulation of reduced H2 and succinate is hypothesized to be the results of adaptation to the rumen environment. Cellulase secretion increased significantly when the molecular chaperone genes ibpA and ibpB were overexpressed. This was also revealed by the transcriptomic data. A possible mechanism for cellulase secretion by E. coli isolates was proposed based on the transcriptomic data and molecular experiments.IMPORTANCE As an important intestinal microorganism, E. coli is present in the intestinal tract of animals and in many other environments. However, it normally does not produce and secret cellulases due to its complex bilayer membrane structure and poor secretory apparatus. Here, we proved that E. coli is widely present in the rumen of sheep and cattle. Systematic analysis of the isolates indicated that they have adapted to the rumen niche, with phenotypes that include secretion of cellulase and fermentative accumulation of succinate and H2 The finding that overexpression of small heat shock protein genes ibpA and ibpB could facilitate cellulase BcsZ secretion, which provides a possible insight into the protein secretion mechanism of rumen-colonizing E. coli.

Bacterial cellulose-derived carbon nanofibers as both anode and cathode for hybrid sodium ion capacitor.

Hybrid ion capacitors (HICs) based on insertion reactions have attracted considerable attention due to their energy density being much higher than that of the electrical double-layer capacitors (EDLCs). However, the development of hybrid ion capacitors with high energy density at high power density is a big challenge due to the mismatch of charge storage capacities and electrode kinetics between the battery-type anode and capacitor-type cathode. In this work, N and O dual doped carbon nanofibers (N,O-CNFs) were combined with carbon nanotubes (CNTs) to compose a complex carbon anode. N,O dual doping effectively tuned the functional group and surface activity of the CNFs while the integration of CNTs increased the extent of graphitization and electrical conductivity. The carbon cathode with high specific surface area and high capacity was obtained by the activation of CNFs (A-CNFs). Finally, a hybrid sodium ion capacitor was constructed by the double carbon electrode, which showed a superior electrochemical capacitive performance. The as-assembled HIC device delivers a maximum energy density of 59.2 W h kg-1 at a power density of 275 W kg-1, with a high energy density of 38.7 W h kg-1 at a power density of 5500 W kg-1.

Identification and characterization of novel xylose isomerases from a Bos taurus fecal metagenome.

Discovering sugar metabolism genes is of great interest for lignocellulosic biorefinery. Xylose isomerases (XIs) were commonly screened from metagenomes derived from bovine rumen, soil, and other sources. However, so far, XIs and other sugar-utilizing enzymes have not been discovered from fecal metagenomes. In this study, environmental DNA from the fecal samples collected from yellow cattle (Bos taurus) was sequenced and analyzed. In the whole 14.26 Gbp clean data, 92 putative XIs were annotated. After sequence analysis, seven putative XIs were heterologously expressed in Escherichia coli and characterized in vitro. The XIs 58444 and 58960 purified from E. coli exhibited 22% higher enzyme activity when compared with that of the native E. coli XI. The XI 58444, similar to the XI from Lachnospira multipara, exhibited a relatively stable activity profile across different pH conditions. Four XIs were further investigated in budding yeast Saccharomyces cerevisiae after codon optimization. Overexpression of the codon-optimized 58444 enabled S. cerevisiae to utilize 6.4 g/L xylose after 96 h without any other genetic manipulations, which is 56% higher than the control yeast strain overexpressing an optimized XI gene xylA*3 selected by three rounds of mutation. Our results provide evidence that a bovine fecal metagenome is a novel and valuable source of XIs and other industrial enzymes for biotechnology applications.

Identification and characterization of an Endo-glucanase secreted from cellulolytic Escherichia coli ZH-4.

BACKGROUND: In the previous study, the cellulolytic Escherichia coli ZH-4 isolated from bovine rumen was found to show extracellular cellulase activity and could degrade cellulose in the culture. The goal of this work was to identify and characterize the secreted cellulase of E. coli ZH-4. It will be helpful to re-understand E. coli and extend its application in industry. RESULTS: A secreted cellulase was confirmed to be endo-glucanase BcsZ which was encoded by bcsZ gene and located in the cellulose synthase operon bcsABZC in cellulolytic E. coli ZH-4 by western blotting. Characterization of BcsZ indicated that a broad range of pH and temperature tolerance with optima at pH 6.0 and 50 °C, respectively. The apparent Michaelis-Menten constant (Km) and maximal reaction rate (Vmax) for BcsZ were 8.86 mg/mL and 0.3 µM/min·mg, respectively. Enzyme activity of BcsZ was enhanced by Mg2+ and inhibited by Zn2+, Cu2+ and Fe3+. BcsZ could hydrolyze carboxymethylcellulose (CMC) to produce cello-oligosaccharides, cellotriose, cellobiose and glucose. CONCLUSIONS: It is confirmed that extracellular cellulolytic capability of E. coli ZH-4 was attributed to BcsZ, which explained why E. coli ZH-4 can grow on cellulose. The endo-glucanase BcsZ from E. coli-ZH4 has some new characteristics which will extend the understanding of endo-glucanase. Analysis of the secretion characteristics of BcsZ provided a great reference for applying E. coli in multiple industrial fields.

Role of surgical treatment for hepatolithiasis-associated intrahepatic cholangiocarcinoma: A retrospective study in a single institution.

CONTEXT: The extent of hepatectomy and lymph node dissection (LND) in the treatment of hepatolithiasis-associated intrahepatic cholangiocarcinoma (HL-iCCA) is still controversial. AIMS: The aim of this retrospective study was to evaluate the role of surgical treatment for HL-iCCA. METHODS: The clinical data of 63 patients with HL-iCCA who undergoing surgery between January 2005 and December 2015 were analyzed retrospectively. STATISTICAL ANALYSIS USED: All data were analyzed by the SPSS 17.0 software program (IMB Inc., Chicago, IL, USA). Survival curves were analyzed by the Kaplan-Meier method and compared by the Log-rank test. A P < 0.05 was considered statistically significant. RESULTS: Forty-nine patients (77.8%) underwent surgical resection including 35 with LND and 14 without LND. The overall 1-, 3-, and 5-year survival rates were 58.1%, 28.2%, and 10.6%, respectively, and the median survival time was 19 months. The 1-, 3-, and 5-year survival rates of resection group were 78.9%, 36.3%, and 13.5%, respectively, while the 1-year survival rate of exploratory laparotomy group was 0 (P < 0.0001). The 1-, 3-, and 5-year survival rates of patients with LND were significantly superior to those of without LND (75.9%, 39.4%, and 20.2% vs. 71.4%, 17.9%, and 0, P = 0.043). According to the N status, the 1-, 3-, and 5-year survival rates of pN0 subgroup were 81.8%, 49.2%, and 28.1%; pN1 subgroup were 65.3%, 18.6%, and 0%; and pNx subgroup were 71.4%, 17.9%, and 0%, respectively (pN0 vs. pN1, P = 0.005; pN0 vs. pNx, P = 0.004; pN1 vs. pNx, P = 0.653). The 1-, 3-, and 5-year survival rates of R0 resection (n = 42) were 80.2%, 36.7%, and 14.9%, respectively, and those of R1 resection (n = 7) were 71.4%, 0%, and 0%, respectively (P = 0.028). CONCLUSIONS: Radical resection is the most effective therapy for HL-iCCA. Regional lymphadenectomy is strongly recommended in resectable HL-iCCA, which is helpful in tumor staging and long-term survival.

An isolated cellulolytic Escherichia coli from bovine rumen produces ethanol and hydrogen from corn straw.

BACKGROUND: Lignocellulosic biomass is the most abundant resource on earth. Lignocellulose is mainly composed of cellulose, hemicelluloses, and lignin. The special construction of three kinds of constituents led to the prevention of effective degradation. The goal of this work was to investigate the great potentials of bovine rumen for novel cellulolytic bacterial isolation, which may be used for chemicals and biofuel production from lignocellulose. RESULTS: A cellulolytic strain, ZH-4, was isolated from Inner Mongolia bovine rumen. This strain was identified as Escherichia coli by morphological, physiological, and biochemical characteristics and 16S rDNA gene sequencing. The extracellular enzyme activity analysis showed that this strain produces extracellular cellulases with an exoglucanase activity of 9.13 IU, an endoglucanase activity of 5.31 IU, and a ß-glucosidase activity of 7.27 IU at the pH 6.8. This strain was found to produce 0.36 g/L ethanol and 4.71 mL/g hydrogen from corn straw with cellulose degradation ratio of 14.30% and hemicellulose degradation ratio of 11.39%. CONCLUSIONS: It is the first time that a cellulolytic E. coli was isolated and characterized form the bovine rumen. This provided a great opportunity for researchers to investigate the evolution mechanisms of the microorganisms in the rumen and provided great chance to produce biofuels and chemicals directly from engineered E. coli using consolidated bioprocess.

MicroRNA-148a suppresses epithelial-mesenchymal transition and invasion of pancreatic cancer cells by targeting Wnt10b and inhibiting the Wnt/ß-catenin signaling pathway.

Epithelial-mesenchymal transition (EMT) plays a critical role in the process of cancer invasion and metastasis. The Wnt/ß-catenin signaling pathway is known as a stimulative factor, which may trigger EMT and metastasis of cancer cells. In addition, several microRNAs (miRNAs) have been proven to regulate the EMT process. Recent research revealed that miR­148a is downregulated in pancreatic cancer. However, the definite role of miR-148a in EMT and invasion of pancreatic cancer is still unknown. The present study attempted to demonstrate the underlying mechanism of miR-148a in the regulation of EMT and invasion of pancreatic cancer cells. Our data revealed that the expression of miR-148a was markedly downregulated in human pancreatic ductal adenocarcinoma (PDAC) cell lines and tissues. In addition, the downregulation of miR-148a was associated with poor prognosis and EMT phenotype. Furthermore, restoration of miR-148a expression inhibited the EMT process, as well as the migration and invasion of BxPC-3 pancreatic cancer cells. Wnt10b, a promoting molecule of the Wnt/ß-catenin signaling pathway, was demonstrated by dual­luciferase reporter assay to be a direct target of miR­148a. Subsequently, we found that miR­148a negatively regulated the protein expression of ß-catenin, cyclin D1 and MMP-9, which were important components of the Wnt/ß-catenin signaling pathway. In conclusion, these findings revealed that miR-148a suppresses EMT and invasion of pancreatic cancer cells by targeting Wnt10b and inhibiting the Wnt/ß-catenin signaling pathway, and thus, miR-148a may serve as a novel therapeutic target for pancreatic cancer.

Laparoscopic left-sided hepatectomy for the treatment of hepatolithiasis: A comparative study with open approach.

BACKGROUND: Hepatolithiasis is a prevalent disease in some regions of China. Left-sided hepatectomy is an effective treatment for left intrahepatic bile duct stones with irreversible disease, such as biliary strictures, severe parenchymal fibrosis or atrophy. However, the advantages of laparoscopic left-sided hepatectomy (LLH) over open approach (OLH) are still controversial. The aim of this study was to compare the clinical outcomes of LLH to those of OLH in the treatment of hepatolithiasis. METHODS: Between January 2013 and October 2016, 75 consecutive patients with hepatolithiasis undergoing left-sided hepatectomy were enrolled in this study. The demographic, intraoperative, and postoperative data were retrospectively analyzed. RESULTS: Among these 75 patients, 36 underwent LLH (LLH group) and 39 underwent OLH (OLH group). The LLH group exhibited a lower intraoperative blood loss (215.8 ± 75.8 vs 298.7 ± 158.9 mL, p = 0.005), intraoperative transfusion (5.6% vs 23.1%, p = 0.032), overall complication rate (13.9% vs 35.9%, p = 0.029), and shorter recovery of bowel movement (2.3 ± 0.8 vs 3.0 ± 1.0 d, p = 0.004), time of off-bed activities (3.2 ± 1.1 vs 5.8 ± 1.4 d, p < 0.001) and postoperative hospital stay (7.7 ± 2.2 vs 10.9 ± 3.3 d, p < 0.001) compared to the OLH group. Similar results were also observed in left lateral sectionectomy and hemihepatectomy subgroups. There was no significant difference in the operative time, initial stone clearance rate, final stone clearance rate, stone recurrence rate and overall cost (All p > 0.05). No perioperative mortality was observed. The conversion rate was 5.6%. CONCLUSION: LLH is a safe and effective treatment for selected patients with hepatolithiasis, with an advantage over OLH in the field of intraoperative blood loss, intraoperative transfusion, overall complication and postoperative recovery.

Laparoscopic Versus Open Left-Sided Hepatectomy for Hepatolithiasis: A Systematic Review and Meta-Analysis.

BACKGROUND: Although laparoscopic left hepatectomy (LLH) for hepatolithiasis had been successfully performed in a series of cases, its advantages over open left hepatectomy (OLH) are still uncertain. This meta-analysis is to compare the clinical outcomes of LLH with those of OLH. MATERIALS AND METHODS: A systematic literature research was performed to identify comparative studies on LLH versus OLH for hepatolithiasis from January 1991 to May 2016. Operative outcomes, postoperative outcomes, and gallstone clearance rate were evaluated. Pooled odds ratios and weighted mean differences with 95% confidence intervals were calculated using fixed-effect or random-effect models. RESULTS: Eight studies, including one randomized controlled trial (RCT) and seven nonrandomized observational clinical studies, met the inclusion criteria. There were 739 patients in this meta-analysis, including 316 LLHs and 423 OLHs. The volume of intraoperative blood loss favored LLH (P = .015). Intraoperative transfusion (P < .001), overall complication (P < .001), and hospital stay (P = .001) were significantly low in LLH. There was no obvious difference in operation time, residual stone rate, and recurrent stone rate. The mean conversion rate was 9.5% (range, 2.2%-15.6%). CONCLUSION: LLH seems to be more effective and safer for selected patients with hepatolithiasis than OLH. As only one RCT was included, the evidence of which is still limited. More prospective, multicenter, and RCTs are needed to further define the real role of the laparoscopic technique in hepatolithiasis.

Isolation of a cellulolytic rod and its potential application in bio-ethanol production / Isolamento de bastão celulítico e sua potencial aplicação na produção de bio-etanol

With the world's focus on bio-fuel, cellulolytic microorganisms are being exclusively explored. In this paper, a strain of rod, NBG, was obtained from the rumen of Inner Mongolia sheep by an enrichment method with Whatman No.1 filter paper as the selective substrate. The strain was found to effectively degrade filter paper in solution. It was identified as Fibrobacter succinogenes based on DNA G + C mol %, together with morphological, physiological and biochemical tests. The endo-glucanase, -glucosidase and filter paper enzyme activity of NBG reached 62.5 ± 3.0 U•mL-1, 169.0 ± 9.4 U•mL-1 and 30.8 ± 5.4 U•mL-1, respectively, within 72 h of fermentation.

Com o foco mundial em biocombustíveis, microrganismos celuloliticos estão sendo exclusivamente explorados. Neste trabalho, uma cepa de bastão, NBG foi obtida do rumen de ovelhas do interior DA Mongolia com o método de enriquecimento e o papel de filtro No.1 como substrato seletivo. A cepa foi encontrada para degradar efetivamente o papel de filtro na solução. Foi identificado como Fibrobacter succinogenes baseado em DNA + c mol% juntamente com testes morofológicos, fisiológico e bioquímicos. A endo-glucanase e o papel de filtro chegaram com relação a atividade de enzima NBG 62.5 ± 3.0 U.ml-1, 169±9.4U.ml-1 e 30.8±5.4U.ml-1, respectivamente, com 72 horas de fermentação.

Production of novel microbial flocculants by Klebsiella sp. TG-1 using waste residue from the food industry and its use in defecating the trona suspension.

A microbial-flocculants-producing (MBF-producing) bacterium, named TG-1, was isolated from waste water of a starch factory, and identified as Klebsiella sp. TG-1. The microbial flocculants (MBF) produced by TG-1, named as MBF-TG-1, was applied to defecating the strong basic trona suspension in the trona industry. After optimizing medium and culturing conditions with single-factor and orthogonal designs, the highest flocculation rate of 86.9% was achieved. Chemical analysis showed that the purified microbial flocculants (MBF-TG-1) was mainly composed of polysaccharides (84.6%), with a small amount of protein or amino acid (11.1%). Bridging mechanism was supposed as the main flocculation mechanism by analyzing the flocculation process and the biochemistry properties of MBF-TG-1. The high flocculation rate (84%) was also achieved with a low-cost medium (the solid residue of tofu production from food industry).