Search

A novel mixotrophic denitrification biofilter for nitrate removal using polycaprolactone and thiosulfate (MD-PT) as electron donors was investigated. MD-PT achieved high nitrate removal efficiency of approximately 99.8 %. The nitrate removal rates of MD-PT reached 1820 g N/m 3 /d, which was 304 g N/m 3 /d higher than that of autotrophic denitrification biofilter using thiosulfate (AD-T). Autotrophic and heterotrophic denitrification pathways in MD-PT were responsible for 67.6-94.5 % and 4.7-32.4 % of the nitrate removal, respectively. The production of SO 4 2- in MD-PT was lower than that in AD-T, and the effluent pH was maintained at approximately 7.3 without acid-base neutralization. The abundance of key genes involved in carbon, nitrogen, and sulfur transformation was enhanced, which improved the nitrate removal of MD-PT. Alicycliphilus and Simplicispira related to organic compounds degradation were enriched after the addition of polycaprolactone. This research provided new insights into mixotrophic denitrification systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

An integrated process of sludge in-situ fermentation, biological phosphorus removal and endogenous denitrification (ISFPR-ED) was developed to treat low ratio of chemical oxygen demand to nitrogen (COD/N) wastewater and waste activated sludge (WAS) in a single reactor. Nutrient removal and WAS reduction were achieved due to Tetrasphaera-dominated sludge fermentation provided organic carbon in extending the anaerobic duration. The WAS reduction efficiency, effluent orthophosphate (PO 4 3- -P) and total inorganic nitrogen reached 28.1 %, less than 0.4 and 7.2 mg/L, respectively. While organic carbon was reduced by 67 %. Tetrasphaera, conventional polyphosphate accumulating organisms (PAOs) stored glycogen, amino acids, and PHA for nutrient removal. Excess energy from fermentation enhanced anaerobic PO 4 3- -P uptake by Tetrasphaera. Tetrasphaera was the dominant PO 4 3- -P removal and fermentation bacteria, working synergistically with conventional PAOs and fermenting microorganisms. This integrated process improves nutrient removal efficiency and reduces operating costs for carbon addition and WAS disposal in wastewater treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In this study, electron transport pathways were activated and diversified by coupling counter-diffusion biofilms with micro-electrolysis for Alizarin yellow R (AYR) denitrogenation. Due to the binding of AYR to two residues of EC 4.1.3.36 with higher binding energy, the expression of EC 4.1.3.36 was down-regulated, causing the EC 3.1.2.28 and EC 2.5.1.74 for menaquinone synthesis (redox mediator) undetectable in Membrane aerated biofilm reactors (MABR). Spontaneous electron generation in the micro electrolysis-coupled MABR (ME-MABR) significantly activated two enzymes. Activated menaquinone up-regulated decolourisation related genes expression in ME-MABR, including azoR (2.12 log 2 ), NQO1 (2.97 log 2 ), wrbA (0.45 log 2 ), and ndh (0.47 log 2 ). The diversified electron flow pathways also promoted the nitrogen metabolism coding genes up-regulation, accelerating further inorganic nitrogen denitrogenation after AYR mineralisation. Compared to MABR, the decolourisation, mineralisation, and denitrogenation in ME-MABR increased by 25.80 %, 16.53 %, and 13.32 %, respectively. This study provides new insights into micro-electrolysis enhanced removal of AYR., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In this study, a microbial fuel cell was constructed using Raoultella sp. XY-1 to efficiently degrade tetracycline (TC) and assess the effectiveness of the electrochemical system. The degradation rate reached 83.2 ± 1.8 % during the 7-day period, in which the system contained 30 mg/L TC, and the degradation pathway and intermediates were identified. Low concentrations of TC enhanced anodic biofilm power production, while high concentrations of TC decreased the electrochemical activity of the biofilm, extracellular polymeric substances, and enzymatic activities associated with electron transfer. Introducing electrogenic bacteria improved power generation efficiency. A three-strain hybrid system was fabricated using Castellaniella sp. A3, Castellaniella sp. A5 and Raoultella sp. XY-1, leading to the enhanced TC degradation rate of 90.4 % and the increased maximum output voltage from 200 to 265 mV. This study presents a strategy utilizing tetracycline-degrading bacteria as bioanodes for TC removal, while incorporating electrogenic bacteria to enhance electricity generation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Utilizing microalgae to capture flue gas pollutants is an effective strategy for mitigating greenhouse gas emissions. However, existing carbon-fixing microalgae exhibit poor tolerance towards acidic flue gas. In this study, the Desmodesmus sp. SZ-1, which can thrive in acidic environments and efficiently sequester CO 2 , was isolated. Desmodesmus sp. SZ-1 exhibited strong acid tolerance ability, with an average carbon fixation rate of 497.6 mg/L/d under 10 % CO 2 and pH 3.5. Physiological analysis revealed that SZ-1 responded to high CO 2 by increasing chlorophyll levels while coping with acidic stress by activating antioxidant enzymes. Genome analysis revealed a large number of carbon fixation and acid adaptation genes, involved in membrane lipid biosynthesis, H + pumps, molecular chaperones, peroxidase system, amino acid synthesis, and carbonic anhydrase. This study provides a novel algal resource for mitigating acid gas emissions and a comprehensive genetic database for genetically modifying microalgae., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The 5-hydroxyectoine is a natural protective agent with long-lasting moisturising and radiation resistance properties. It can be naturally synthesized by some extremophiles using the "bacterial milking" process, but this can corrode bioreactors and downstream purification may cause environmental pollution. In this study, an engineered Escherichia coli (E. coli) strain was constructed for the 5-hydroxyectoine production. First, three ectoine hydroxylases were characterised and the enzyme from Halomonas elongata was the most effective. The L-2,4-diaminobutyrate transaminase mutant was introduced into the engineered strain, which could accumulate 2.8 g/L 5-hydroxyectoine in shake flasks. By activating the glyoxylate cycle and balancing the α-ketoglutarate distribution, the 5-hydroxyectoine titer was further increased to 3.4 g/L. Finally, the optimized strain synthesized 58 g/L 5-hydroxyectoine via a semi-continuous feeding process in a NaCl-free medium. Overall, this study reported the highest titer of 5-hydroxyectoine synthesized by E. coli and established a low-salt fermentation process through the aforementioned efforts., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

As the highest-demand vitamin, the development of a one-step vitamin C synthesis process has been slow for a long time. In previous research, a Gluconobacter oxydans strain (GKLG9) was constructed that can directly synthesize 2-keto-L-gulonic acid (2-KLG) from glucose, but carbon source utilization remained low. Therefore, this study first identified the gene 4kas (4-keto-D-arabate synthase) to reduce the loss of extracellular carbon and inhibit the browning of fermentation broth. Then, promoter engineering was conducted to enhance the intracellular glucose transport pathway and concentrate intracellular glucose metabolism on the pentose phosphate pathway to provide more reducing power. Finally, by introducing the D-sorbitol pathway, the titer of 2-KLG was increased to 38.6 g/L within 60 h in a 5-L bioreactor, with a glucose-to-2-KLG conversion rate of about 46 %. This study is an important step in the development of single-bacterial one-step fermentation to produce 2-KLG., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Nitrite as an important substrate for Anammox can be provided by partial denitrification (PD). In this study, endogenous partial denitrification (EdPD) and exogenous partial denitrification (ExPD) sludge were domesticated and their nitrite transformation rate reached 74.4% and 83.4%, respectively. The impact of four carbon/nitrogen (C/N) ratios (1.5, 3.0, 5.0 and 6.0) on nitrous oxide (N 2 O) emission and denitrification functional genes expression in both PD systems were investigated. Results showed that elevated C/N ratios enhanced most denitrification genes expression, but in EdPD, high nitrite levels suppressed nosZ genes expression (from 9.4% to 1.4%), leading to increased N 2 O emission (0 to 3.4%). EdPD also exhibited lower electron transfer system activity, resulting in slower nitrogen oxide conversion efficiency and more stable nitrite accumulation compared to ExPD. These findings offer insights for optimizing PD systems under varying water quality conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Squalene, a high-value acyclic triterpenoid compound, is broadly used in the food and medical industries. Although the large acetyl-CoA pool and hydrophobic space of Yarrowia lipolytica are suitable for the accumulation of squalene, the current production level in Y. lipolytica is still not sufficient for industrial production. In this study, two rounds of multicopy integration of genes encoding key enzymes were performed to enhance squalene anabolic flux in the cytoplasm. Furthermore, the mevalonate pathway was imported into peroxisomes through the compartmentalization strategy, and the production of squalene was significantly increased. By augmenting the acetyl-CoA supply in peroxisomes and the cytoplasm, the squalene was boosted to 2549.1 mg/L. Finally, the squalene production reached 51.2 g/L by fed-batch fermentation in a 5-L bioreactor. This is the highest squalene production reported to date for microbial production, and this study lays the foundation for the synthesis of steroids and squalene derivatives., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Applications of post-denitrification processes are subjected to low reaction rates caused by a lack of carbon resources. To offer a solution for reaction rate promotion, this research found a pilot-scale anaerobic/aerobic/anoxic bioreactor treating 55-120 m 3 /d low-strength municipal wastewater for 273 days. A short hydraulic retention time (HRT, 5-6 h) and a high nitrogen removal rate (63.2 ± 9.3 g-N/m 3 ·d) were achieved using HRT optimization. The effluent total nitrogen concentration was maintained at 5.8 ± 1.4 mg/L while operating at a high nitrogen loading rate of 86.2 ± 12.8 g-N/m 3 ·d. The short aeration (1.25-1.5 h) minimized the Glycogen loss. The endogenous denitrification rate increased to above 1.0 mg/(g-VSS·h). The functional genus Ca. Competibacter enriched to 2.3 %, guaranteeing the efficient post-denitrification process. Dechloromonas rose to 1.1 %, aiding in the synchronous phosphorus removal. These findings offered fresh insights into AOA processes to achieve energy/cost-saving wastewater treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Heavy metal-resistant bacteria secrete extracellular proteins (e-PNs). However, the role of e-PNs in heavy metal resistance remains elusive. Here Fourier Transform Infrared Spectroscopy implied that N-H, C = O and NH 2 -R played a crucial role in the adsorption and resistance of Ni 2+ in the model organism Cuprividus pauculus 1490 (C. pauculus). Proteinase K treatment reduced Ni 2+ resistance of C. pauculus underlining the essential role of e-PNs. Further three-dimension excitation-emission matrix fluorescence spectroscopy analysis demonstrated that tryptophan proteins as part of the e-PNs increased significantly with Ni 2+ treatment. Proteomic and quantitative real-time polymerase chain reaction data indicated that major changes were induced in the metabolism of C. pauculus in response to Ni 2+ . Among those lipopolysaccharide biosynthesis, general secretion pathways, Ni 2+ -affiliated transporters and multidrug efflux play an essential role in Ni 2+ resistance. Altogether the results provide a conceptual model for comprehending how e-PNs contribute to bacterial resistance and adsorption of Ni 2+ ., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Ectoine, a natural protective agent, is naturally synthesized at low titers by some extreme environment microorganisms that are usually difficult to culture. There is a need for an efficient and eco-friendly ectoine production process. In this study, Escherichia coli BL21(DE3) with the ectABC gene cluster from Halomonas venusta achieved 1.7 g/L ectoine. After optimizing the expression plasmid, 2.1 g/L ectoine was achieved. Besides, the aspartate kinase mutant LysC T311I from Corynebacterium glutamicum and aspartate semialdehyde dehydrogenase from Halomonas elongata were overexpressed to increase precursors supply. Furthermore, the rate-limiting enzyme EctB was semirationally engineered, and the E407D mutation enhanced ectoine production by 13.8 %. To improve acetyl-CoA supply, the non-oxidative glycolysis pathway was introduced. Overall, the optimized strain ECT9-5 produced 67.1 g/L ectoine by fed-batch fermentation with a 0.3 g/g of glucose and the kinetic model resulted in a good fit., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Direct production of 2-keto-L-gulonic acid (2-KLG, the precursor of vitamin C) from D-glucose through 2,5-diketo-D-gluconic acid (2,5-DKG) is a promising alternative route. To explore the pathway of producing 2-KLG from D-glucose, Gluconobacter oxydans ATCC9937 was selected as a chassis strain. It was found that the chassis strain naturally has the ability to synthesize 2-KLG from D-glucose, and a new 2,5-DKG reductase (DKGR) was found on its genome. Several major issues limiting production were identified, including the insufficient catalytic capacity of DKGR, poor transmembrane movement of 2,5-DKG and imbalanced D-glucose consumption flux inside and outside of the host strain cells. By identifying novel DKGR and 2,5-DKG transporter, the whole 2-KLG biosynthesis pathway was systematically enhanced by balancing intracellular and extracellular D-glucose metabolic flux. The engineered strain produced 30.5 g/L 2-KLG with a conversion ratio of 39.0%. The results pave the way for a more economical large-scale fermentation process for vitamin C., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

This study constructed two thiosulfate-driven autotrophic denitrification biofilters filled with volcanic rock (VR-BF), sponge iron and volcanic rock (SIVR-BF), respectively. The nitrate removal load (3200 g/m 3 /d) and efficiency (98 %) of SIVR-BF were higher than those of VR-BF. The removal of phosphate in SIVR-BF was mainly through forming FePO 4 and Fe 3 (PO 4 ) 2 (OH) 2 . Sulfur and iron cycles in SIVR-BF contributed to Fe (II)/Fe (III) electron shuttle, as well as S 2- , S 0 , Sn 2- electron buffer and energy storage, which improved nitrate removal and electron utilization. The formation of multi-path collaborative denitrification dominated by sulfur autotrophic denitrification (64.2 ∼ 89.6 %) in SIVR-BF. The other denitrification pathways, such as iron autotrophic denitrification, which buffered pH and reduced sulfate production. Thiobacillus (38.6 %) and Ferritrophicum (25.3 %) were the dominant genus of VR-BF and SIVR-BF, respectively, which played crucial roles in autotrophic denitrification of iron and sulfur. SIVR-BF was a promising process to realize iron-sulfur coupling autotrophic denitrification and phosphate removal., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The objective of this work was to evaluate the fungal community assembly and function during food waste composting with Aneurinibacillus sp. LD3 (LD3) inoculant. Inoculation reduced the content of total organic carbon, moisture content, nitrate nitrogen, and nitrite nitrogen. The LD3 inoculant was able to drive the changes in the assembly of the fungal community. In particular, inoculation with LD3 not only increased the relative abundance of Ascomycota and Trichocomaceae_unclassified for lignocellulose degradation at the mesophilic and cooling stages but also reduced the relative abundances of the opportunistic human pathogen Candida. Saprotroph was the predominant fungal trophic mode in composting, and inoculation with LD3 has a better inactivation effect on animal and plant pathogenic fungi during composting. Furthermore, the variation of the fungal community after inoculation with LD3 was the largest explained by temperature (30.64%). These results implied that LD3 significantly regulated fungal composition and function of food waste composting., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

This work explored the microbial mechanisms for the improvement of composting efficiency driven by thermotolerant lignin-degrading bacterium Aneurinibacillus sp. LD3 (LD3). Results showed that LD3 inoculant prolonged the thermophilic period by 4 days, improved the final content of humic acid, total phosphorus (TP), nitrogen, potassium and seed germination index. Inoculating LD3 enhanced the relative abundance of thermotolerant and phosphate-solubilizing microbes including the phyla of Proteobacteria, Bacteroidota, Firmicutes, and Actinobacteriota, and the genus of Bacillus, Thermoactinomyces, and Pseudomonas. Metabolic function analysis showed that sequences involved in carbohydrate and amino acid metabolism were boosted, while sequences associated with human disease were reduced after inoculating LD3. Spearman correlation analysis revealed that Aneurinibacillus has a significant positive correlation with temperature, TP, Bacillus, and Thermoactinomyces. This study provides useful information for understanding the microbial mechanisms of LD3 promoting composting efficiency, and reveals the tremendous potential of LD3 in the resource utilization of organic solid wastes., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

As the sole energy for photosynthesis, light decrease rapidly with path due to absorption by pigments and scattering by cells in microalgal suspensions. By comprehensively considering cell concentrations, pigment components, and light spectra, a modified Cornet model for light transmission in microalgal suspensions is established. The developed model better fits experimental data with a higher adjusted R 2 , which is 5% higher than the model that is based only on cell concentration. The attenuation of blue light is the most severe, followed by red and green light. Among the three main pigments, total carotenoids contribute the most to the absorption of blue and green light (with contribution coefficients of 89.26 ± 4.53% and 46.04 ± 3.77%, respectively), and chlorophyll a contributes the most to the absorption of red light (with a contribution coefficient of 75.33 ± 5.08%). This study provides a better understanding and prediction of light transmission during microalgal cultivation., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Acetyl-CoA is a kind of important cofactor that is involved in many metabolic pathways. It serves as the precursor for many interesting commercial products, such as terpenes, flavonoids and anthraquinones. However, the insufficient supply of acetyl-CoA limits biosynthesis of its derived compounds in the intracellular. In this review, we outlined metabolic pathways involved in the catabolism and anabolism of acetyl-CoA, as well as some important derived products. We examined several strategies for the enhanced supply of acetyl-CoA, and provided insight into pathways that generate acetyl-CoA to balance metabolism, which can be harnessed to improve the titer, yield and productivities of interesting products in Saccharomyces cerevisiae and other eukaryotic microorganisms. We believe that peroxisomal fatty acid β-oxidation could be an attractive strategy for enhancing the supply of acetyl-CoA., (Copyright © 2021. Published by Elsevier Ltd.)

Sponge iron is a potential material for nitrogen and phosphate removal. To explore the performances and mechanisms of nitrogen and phosphate removal by sponge iron, a sponge iron biofilter was established. The results showed that nitrate was completely removed at HRT of 48 h without external carbon source and at HRT of 3 h with C/N ratio of 5. Furthermore, it was easy to achieve partial denitrification at HRT of 1 h with C/N ratio of 3. The mechanisms of nitrate removal were chemical reduction and nitrate dependent ferrous oxidation without external carbon source and heterotrophic denitrification with external carbon source. XPS result indicated that phosphate was removed by the formation of ferric phosphate precipitation. High throughput sequencing showed that iron-oxidizing bacteria Gallionellaceae was highly enriched in biofilter, accounting for 17.83%, which indicated that it was feasible to achieve autotrophic nitrate removal by sponge iron biofilter., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Microbial fuel cells (MFCs) are promising equipment for simultaneous treatment of sewage and power generation. External resistance (R ext ) plays a crucial impact in the performance of MFCs in antibiotic wastewater treatment and antibiotic resistance genes (ARGs) reduction. In this study, R ext and whether to add 20 mg/L sulfamethoxazole (SMX) as variables, it was observed that the performance of several chemical properties of MFCs was optimal when R ext was 1000 Ω. The power density before and after addition of SMX was 1220.5 ± 24.5 mW/m 2 and 1186.2 ± 9.2 mW/m 2 , respectively; Furthermore, the degradation rate of SMX was as high as 87.52 ± 1.97% within 48 h. High-throughput sequencing results showed that both R ext and SMX affected the microbial community and relative abundance of the phylum and genera. Meanwhile, the MFCs with 1000 Ω R ext generated less the targeted ARGs. Experimental results showed that 1000 Ω was the most suitable R ext for MFCs in the treatment of antibiotic wastewater., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

One of the goals of metabolic engineering is to engineer strains that can optimally produce target metabolites. However, the current workflow for rational engineering of the metabolic pathway is sometimes time-consuming and labor-intensive. Here, we have established a cost-effective approach for screening for variants secreting metabolites. Different surface display systems were adopted and verified, which anchored pHluorin to the Candida glabrata cell surface to associate pyruvic acid detection with the read out of this reporter. A generalizable simulation approach based on computational fluid dynamics and regularity of generated droplet dimension was presented, which was found to be an efficient design tool to explore microfluidic characteristics or optimization. Finally, a microfluidic platform based on simulation coupled with surface display system was constructed. A mutant exhibiting a 73.6% increase in pyruvic acid production was identified. This ultrahigh-throughput screening pattern offers a practical guide for identifying microbial strains with many traits of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The 2-keto-L-gulonic acid (2-KLG) is the direct precursor for industrial vitamin C production. The main biosynthetic method for 2-KLG production is the classical two-step fermentation route. However, disadvantages of this method are emerging, including high consumption of energy, difficulties in strain screening, complex operation, and poor stability. In this study, five recombinant Escherichia coli strains overexpressing different sorbose/sorbosone dehydrogenases were constructed and used for 2-KLG production. By optimizing catalytic conditions and further expressing pyrroloquinoline quinone in the recombinant strain, the titer of 2-KLG reached 72.4 g/L, with a conversion ratio from L-sorbose of 71.2% in a 5-L bioreactor. To achieve direct biosynthesis of 2-KLG from D-sorbitol, a co-culture system consisting of Gluconobacter oxydans and recombinant E. coli was designed. With this co-culture system, 16.8 g/L of 2-KLG was harvested, with a conversion ratio from D-sorbitol of 33.6%. The approaches developed here provide alternative routes for the efficient biosynthesis of 2-KLG., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

2-Phenylethanol (2-PE) is an important high-grade aromatic alcohol, which is widely used in the cosmetics, perfumery and food industries. However, 2-PE is mainly synthesized using a chemical route, which produces environmental pollution and harmful by-products. Screening of high-yielding wild-type strains has become an important goal for the future biosynthesis of 2-PE. In this study, a wild-type Wickerhamomyces anomalus was isolated from rice wine fermented mash. By optimizing the initial glucose and l-phenylalanine concentrations, 2630.7 mg/L of 2-PE was obtained in shaking flasks. The conditions of initial glucose and l-phenylalanine concentration, pH, and inoculation amount were optimized for 2-PE production with W. anomalus. Finally, based on the optimal conditions, the 2-PE titer reached 4,727.3 mg/L by a single-dose fed-batch strategy in a 5-L bioreactor. The results showed that the ability was expanded to harness the Ehrlich pathway for the production of high-value aromatics in aroma-producing yeast species., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The dynamic response mechanism of Candidatus Accumulibacter clades to environmental factors in enhanced biological phosphorus removal (EBPR) was unclear. This study investigated the relationship between the transcriptional responses of Candidatus Accumulibacter clades and environmental dynamics. Results suggested that Candidatus Accumulibacter clade IIA only responded in initial 20 and 30 min of P-release and P-uptake stage, respectively, and was also the first clade to stop responding among the six Candidatus Accumulibacter clades. Clade IIC and IID responded at rising stage of P-release and P-uptake rate. Clade IA and IIB responded at decreasing stage of P-release and P-uptake rate. The transcriptional response duration of clade IIF was the longest, which constantly responded throughout anaerobic, anoxic and oxic phase. The transcriptional responses of Candidatus Accumulibacter clades to environmental dynamics revealed the microorganisms actually working in P-release and P-uptake, and gave a new insight into the transcriptional responses related to the EBPR performance., Competing Interests: Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In this study, a novel Aureobasidium pullulans GXL-1 strain without melanin secretion was isolated for efficient polymalic acid (PMA) production. The PMA produced by GXL-1 was characterized, and its molecular mass was determined to be 1.621 kDa by gel permeation chromatography. Liquefied corn starch was shown to replace glucose for PMA production by GXL-1 through simultaneous saccharification and fermentation. The PMA titer obtained from batch fermentation was up to 49.0 ± 1.6 g/L in a 10 L fermentor, and the PMA yield and productivity obtained from repeated-batch fermentation were up to 0.50 g/g and 0.34 g/L·h, respectively. Furthermore, process design and techno-economic analysis were performed at an annual output level of 5000 metric tons by SuperPro Designer. Results showed that the production cost of $2.046/kg and payback period of 6.9 years were achieved by repeated-batch fermentation; this provides an economically feasible strategy for industrial-scale production of PMA., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The microbial community in endogenous denitrification and denitrifying phosphorus removal treatment at transcription level was unknown. This study first confirmed the expression of actually active bacteria in endogenous denitrification and denitrifying phosphorus removal system to treat low C/N municipal wastewater. No external carbon source was added to influent wastewater. The cDNA high throughput sequencing showed that Candidatus Accumulibacter was the most effective polyphosphate accumulating organisms (PAOs) that actually worked rather than Dechloromonas, which was different from the result at gene level. Reverse transcriptional PCR (RT-PCR) and analysis of Variance (ANOVA) suggested that the ratios of dead or dormant bacteria could monitor wastewater treatment process. Identification of active microbial community at transcription level demonstrated that the synergy of endogenous denitrification by glycogen accumulating organisms (GAOs) and denitrifying phosphorus removal by Candidatus Accumulibacter fully utilized the internal carbon source, and effectively solved the problem of carbon source deficiency in municipal wastewater treatment., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Polyaluminium chloride (PAC) was added into the biological phosphorus removal (BPR) systems to investigate the populations of polyphosphate and glycogen accumulating organisms (PAOs and GAOs). Typical BPR performed under Al:P of 1:1, while BPR almost disappeared at Al:P of 4:1. Even with high PAC addition, PAOs still existed in systems. Compared to the BPR with no PAC addition, the relative abundance of Accumulibacter, Tetrasphaera and Commnadaceae slightly increased with PAC addition. The relative abundance of Dechloromonas was improved from 0.87% to 3.82%, becoming the most dominant PAOs. The specific structures of Accumulibacter and Tetrasphaera changed little, but that of Dechloromonas and Comamonadaceae significantly altered. Regarding the GAOs, the relative abundance of Competibacter and Defluviicoccus significantly declined. Additionally, PAC addition effectively inhibited the proliferation of filamentous bacteria, indicating its potential in inhibiting the sludge filamentous bulking. This study provided guidance for the selection of the phosphorus removal process and operational conditions., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Dissolved oxygen (DO) supply plays essential roles in microbial organic acid production. Candida glabrata, as a dominant strain for producing pyruvic acid, principally converts glucose to pyruvic acid through glycolysis. However, this process relies excessively on high extracellular DO content. In this study, in combination with specific motif analysis of gene promoters, hypoxia-inducible factor 1 (HIF1) was engineered to improve the transcription level of some enzymes related to pyruvic acid synthesis under low DO level and directly led to increased pyruvic acid production and glycolysis efficiency. Moreover, the intracellular stability of HIF1 was further optimized from different aspects to maximize pyruvic acid accumulation. Finally, the pyruvic acid titer in a 5-L batch bioreactor with 10% DO level reached 53.1 g/L. As pyruvic acid is involved in the biosynthesis of various products, these findings suggest that HIF1-enabled regulation method has significant potential for increasing the synthesis of other chemicals in microorganisms., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

As a stable microbial polysaccharide, scleroglucan has extensive application in the food, medicine, and cosmetics industries. However, its large-scale industrial application is limited by its high production cost, low yield, long production time, etc. This study aims to enhance scleroglucan production by Sclerotium rolfsii WSH-G01. Based on the analysis of batch fermentation kinetics parameters, a pH-shift strategy was adopted. Through systematic kinetics analysis, a 32.4 g/L scleroglucan was accomplished. The kinetic model of the pH-shift batch fermentation process was established using a logistic equation, Luedeking-Piret equation, and a Luedeking-Piret-like equation. As decreased glucose concentration could cause decreased scleroglucan synthesis rates during the batch fermentation process, 30 g/L glucose was fed in the later phase of fermentation. As a result, scleroglucan production increased to 42 g/L, with a productivity of 0.5 g/L·h. Thus, the pH-shift strategy and feeding approach could be useful for industrial scleroglucan production., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Co-production of α-ketoglutaric acid (KGA) and pyruvic acid (PYR) by Yarrowia lipolytica WSH-Z06 could significantly increase the final titer and yield of keto acids. However, efficient separation of KGA and PYR in an economic manner is a big challenge owing to their similar properties. In the present study, a separation process was established to convert PYR in the fermentation broth to l-tyrosine (TYR). Owing to its low solubility, TYR was easily precipitated out and could be easily removed from the reaction system. The whole-cell catalysis reaction solution was subjected to acid treatment, centrifugation, cation exchange column separation, rotary evaporation, Buchner funnel filtration, and dry separation method to obtain KGA and TYR powders. The purity/recovery rates of KGA and TYR were 98.16%/78.68% and 98.19%/73.46%, respectively. The use of biological pathways to separate KGA from the culture broth could make the separation process easier and further decrease the operation cost., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Herba Epimedii is a traditional Chinese herbal medicine that contains a mixture of bioactive flavonoid glycosides. Among them, icariin has the most outstanding bioactive functions, while epimedin C exhibits substantial toxicity. A recombinant α-L-rhamnosidase ( syn AnRhaE) from Aspergillus nidulans was expressed in Escherichia coli to promote the efficient bioconversion of epimedin C to icariin. A hydrolase activity of 574.5 U L -1 was acquired via optimized fed-batch fermentation in a 5-L bioreactor. The enzyme proved to be stable in an acidulous pH range below 55 °C with an optimal pH of 4.5 and optimal temperature of 55 °C. Epimedin C (1 g L -1 ) was 100% converted to icariin within 90 min using recombinant cells. The resting cells proved to be selective for epimedin C and 2″-O-rhamnosylicariside II in crude extracts of the epimedium plant. This work provides an original and efficient biocatalyst system that can be applied in industrialized production of icariin., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In biological municipal wastewater treatment, gene level analysis of community structure could not determine functional genes that actually played a role and expression of viable microorganism. In this study, reverse transcriptional PCR (RT-PCR), cDNA high throughput sequencing and transcriptional activity analysis were conducted to investigate active microbial community with nitrogen and phosphorus removal from municipal wastewater. RT-PCR and correlation heatmap analysis suggested that transcriptional activities of bacteria had strong correlation with performance of nitrogen and phosphorus removal, they might be therefore regarded as an indicator for wastewater treatment monitoring. When DO concentration were raised from 0.6 mg/L to 2 mg/L and C/N ratio from 3-4 to 5, the increase of population abundance and transcriptional activities of denitrifying genes improved the removal efficiencies of COD and TN. The species with relatively high abundance at gene level were not really active species at transcription level, and vice versa., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Malt syrup, as a low-cost substrate without any pretreatment, was proved to be able to replace maltose for ploymalic acid (PMA) production by Aureobasidium melanogenum GXZ-6. The PMA titer of 55.53 ± 1.72 g/L was obtained by batch fermentation in a 10-L fermentor with addition of malate, citrate and sodium malonate. Then, a higher PMA titer of 124.07 ± 2.28 g/L was obtained in fed-batch fermentation, which increased by 123.43% than that from batch fermentation. Moreover, repeated-batch fermentation with three batches gave a PMA titer of 64.06 g/L on average with a higher yield of 0.81 g/g and productivity of 0.56 g/L·h. Fermentation process and economics analysis were performed by SuperPro Designer for a 2000 metric tons plant. Results showed that PMA production cost was as low as $ 1.716/kg by fed-batch fermentation, which provides an economical strategy for large-scale PMA production., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Achieving nitritation is a prerequisite to promote nutrients removal and save energy, but emission of nitrous oxide as a greenhouse gas cannot be ignored. This study established the nitritation in a continuous-flow MUCT process and investigated the mechanism of N 2 O generation. The nitrite accumulation ratio (NAR) reached 95% by controlling the low DO of 0.3-0.5 mg/L and short HRT of 8 h. The 15 N-isotope tracer experiment indicated that the percentage of nitrifier-denitrification (ND) pathway increased by 12.7% under the limited-aeration mode, improving the stable operating of nitritation. Meanwhile, the autotrophic anammox pathway increased with the contribution ratio of 14.7% to N 2 emission under the nitritation mode. The 15 N-DNA-SIP revealed that the Nitrosomonas executed the ND pathway and the Planctomycetes conducted the anammox process, respectively. The integration of autotrophic and heterotrophic process based on nitritation technique has potential to solve the carbon-limited issue for total nitrogen removal in mainstream WWTPs., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In order to solve the technical bottleneck that the biomass yield and lipid accumulation cannot be increased simultaneously during microalgae growth, a heterotrophic-assisted photoautotrophic biofilm (HAPB) growth mode of Chlorella vulgaris was constructed. The light penetration capability of the microalgae biofilm formed through heterotrophic-assisted photoautotrophic growth was 64% stronger than that formed by photoautotrophic growth. Due to the different demands of autotrophic and heterotrophic growth of microalgae, the nutrient environment and growth conditions were optimized to fully utilize the advantages and potentials of the HAPB culture model. An optimized molar ratio of total inorganic carbon (CO 2 ) to total organic carbon (glucose) (20:1) and a molar ratio of total carbon to total nitrogen (72:1) were obtained. The maximum specific growth rate of Chlorella vulgaris increased by 78% compared to that before optimization. Meanwhile, the lipid content and yield increased by 120% and 147%, respectively, up to 47.53% and 41.95 g m -2 ., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Both α-ketoglutarate (α-KG) and pyruvate (PYR) are important organic acids with promising applications in the food, pharmaceutical and chemical industries. During the production of α-KG by different microorganisms, PYR is always present as a by-product. Strategies have been applied to eliminate PYR accumulation since it can bring difficulties to the downstream separation process. However, modern separation technologies have already conquered this problem. Therefore, this study was aimed at simultaneously enhancing α-KG and PYR production by Yarrowia lipolytica WSH-Z06. Using a fed-batch strategy, in which the initial glycerol concentration was 50g·L -1 , the residual glycerol concentration was maintained 20-30g·L -1 by constant feeding at a rate of 1.25g·L -1 ·h -1 . The titers of α-KG and PYR were increased by 9.6% and 176.8%, and reached 67.4g·L -1 and 39.1g·L -1 , respectively. The final yield of keto acids was 0.71g·g -1 glycerol, which is 42.0% higher than that of the optimal batch fermentation., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Relevance of clade-level population dynamics of "Candidatus Accumulibacter" to performance of denitrifying phosphorus (P) removal from municipal wastewater was investigated. Stable denitrifying P removal in anoxic zone of continuous-flow reactor was achieved, accounting for 90% of total P removal. Clades IIC and IIF affiliated with Accumulibacter lineage were the dominant clades during denitrifying P removal, reaching 90% of ppk1 clone library. NarG gene library indicated Gamma and Beta-proteobacteria played an important role in nitrate reduction. Diversity and abundance of nirS library was much more than nirK, and thus became the main functional gene to execute nitrite reduction. Based on abundance of nirS, nirK and ppk1, the ratio of Accumulibacter capable of denitrifying P removal to total Accumulibacter was 22%. No matter whether Accumulibacter had narG gene or not, high abundance of narG at a level of 10(9)cells/(g dried-sludge) promoted nitrate reduced to nitrite, ensuring performance of denitrifying P removal., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

High nutrients removal above 90% from carbon-limited municipal sewage was obtained without adding external carbon source. Achieving nitritation was a prerequisite to improve nutrients removal. Denitrifying phosphorus (P) removal using nitrite as electron acceptor was the key pathway in anoxic zone, where nitrogen removal reached above 60% and average denitrifying P removal was 88%. Simultaneous nitritation/denitritation and anaerobic ammonia oxidation (anammox) possibly contributed to nitrogen removal of 26-36% in aerobic zone. Quantitative PCR assays presented that the abundance of anammox bacteria under nitritation was more than that under complete nitrification. The largest amount of anammox bacteria was 1.32×10(6)copies/gVSS, about 5.6 times increase over a period of 255days. Nitrite concentration of 17mg/L in aerobic zone inhibited anammox bacteria. Quantitative results suggested possible occurrence of anammox. Based on performance of nitritation, combining heterotrophic denitrification with autotrophic nitrogen removal is an effective strategy to improve nutrients removal from carbon-limited wastewater., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Population dynamic of nitrifying bacteria was investigated for nitrogen removal from municipal wastewater. Nitritation was established with nitrite accumulation ratios above 85%. Quantitative PCR indicated that Nitrospira was dominant nitrite oxidizing bacteria (NOB) and Nitrobacter was few. During nitritation achieving, Nitrobacter was firstly eliminated, along with inhibition of Nitrospira bioactivities, then Nitrospira percentage declined and was finally washed out. Nitritation establishment depended on inhibiting and eliminating of NOB rather than ammonia oxidizing bacteria (AOB) enriching. This is the first study where population dynamics of Nitrobacter and Nitrospira were investigated to reveal mechanism of nitritation in a continuous-flow process. Phylogenetic analysis of AOB indicated that Nitrosomonas-like cluster and Nitrosomonas oligotropha were dominant AOB, accounting for 81.6% of amoA gene clone library. Community structure of AOB was similar to that of complete nitrification system with long hydraulic retention time, but different from that of nitritation reactor with low DO concentration., (Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The shift of microbial community under the adjustment of different pH was analyzed by denaturing gradient gel electrophoresis (DGGE). The results indicated, at initial pH 1.0, 2.0 and 3.0, the copper extraction in 22 days amounted to 84.6%, 88.2% and 77.5%, respectively; however, when the initial pH was 2.0, processing pH was adjusted to 1.0 and 3.0 on day 16, the copper extraction in 32 days was 85% and 62.6%, respectively. DGGE analysis showed Acidithiobacillus caldus, Leptospirillum ferriphilum, Sulfobacillus thermosulfidooxidans and Ferroplasma thermophilum existed in bioleaching systems. At initial pH 1.0 and 3.0, S. thermosulfidooxidans and A. caldus were main microorganisms. While at initial pH 2.0, L. ferriphilum, A. caldus and S. thermosulfidooxidans were always detected. At processing pH 1.0 and 3.0, the adjustment of pH greatly inhibited the growth of L. ferriphilum; it was also found microbial community would recover gradually only if pH stimulation did not fatally affect microorganisms., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

A thermophilic strain Bacillus subtilis GXA-28 with capability of γ-PGA production was characterized, and its product was identified. The effect of temperatures on cell growth, γ-PGA yield and molecular weight were investigated. Results showed that γ-PGA yield reached 19.92g/L at 45°C with a high productivity of 0.91g/L/h, and the molecular weight reached 3.03×10(6)Da. Then, the flux distribution and the key enzyme activities at 2-oxoglutarate branch under specified temperature were determined to illustrate the possible metabolic mechanism contributing to the improved γ-PGA production. Results indicated that the fluxes from iso-citrate to 2-oxoglutarate and from 2-oxoglutarate to glutamate were increased with high activity of isocitrate dehydrogenase and glutamate dehydrogenase, which led to enhance γ-PGA production. This work firstly employed temperature control strategy to improve γ-PGA production, and provided novel information on the metabolic mechanism of γ-PGA biosynthesis in Bacillus species., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Nitritation and denitrifying P removal under mode of nitritation and nitrification was investigated in continuous MUCT process treating domestic wastewater. Nitritation was established through short hydraulic retention time to 6 h and low dissolved oxygen concentration of 0.3-0.5 mg/L. Nitritation was stabilized for 95 days with average nitrite accumulation ratio over 90%. Ammonia and total nitrogen removal under nitritation reached 99% and 83%, respectively, much better than complete nitrification. Real-time quantitative PCR assays presented that cell numbers and percentages of ammonia oxidizing bacteria (AOB) population had a clear correlation with nitrite accumulation ratios. The highest percentage of AOB was 13% of total bacterial population. P removal was mainly completed by denitrifying P removal of about 90% occurring in anoxic zone. The P removal efficiency under nitritation was 30% higher than that under complete nitrification. Denitrifying P removal under nitritation was highly beneficial to the treatment of wastewater with limiting carbon source., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Poly(γ-glutamic acid), as a naturally occurring homopolymer, is widely used in industry, agriculture, food and medicine. Fibrinolytic enzyme has a great potential for the prevention and/or treatment of vascular diseases caused by fibrin clots. Co-production of γ-PGA and fibrinolytic enzyme by Bacillus subtilis GXA-28 (CCTCC M 2012347) from soybean residue using cane molasses and monosodium glutamate waste liquor under sterilized and non-sterilized condition were investigated. It was observed that total sugar from cane molasses of 3% (w/w) and glutamate from monosodium glutamate waste liquor of 2% (w/w) were favorable for γ-PGA and fibrinolytic enzyme co-production at pH 7.0 and 45°C. Based on the optimal medium, the γ-PGA and fibrinolytic activity reached 103.5 g/kg-substrates at 22 h and 986 U/g-substrates at 24h under non-sterilized condition, respectively. To our knowledge, the yield of γ-PGA was highest in all reported literatures., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

A defined mixed moderately thermophilic consortium including three terrestrial microorganisms (Leptospirillum ferriphilum, Acidithiobacillus caldus and Ferroplasma thermophilum) and a marine acidophilic halotolerant bacterium (Sulfobacillus sp. TPY) was constructed to evaluate its ability for bioleaching of chalcopyrite with the addition of sodium chloride (NaCl), and the community dynamics was monitored by real-time quantitative PCR (qPCR). It was found that Sulfobacillus sp. TPY was able to tolerate 2% (w/v) NaCl, while other three microorganisms were suppressed when the concentration of NaCl was higher than 0.35%. The results suggested that NaCl below certain concentration could improve copper extraction by using pure cultures or the consortium to bioleach chalcopyrite. Community dynamics analysis during bioleaching at 0.1% NaCl showed that Sulfobacillus sp. TPY was predominant species during the whole bioleaching process, L. ferriphilum and A. caldus were less at any time compared with Sulfobacillus sp. TPY. F. thermophilum had never been dominant species even in the final stage., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

A consortium of microorganisms from acid mine drainage samples was cultured in modified 9 K medium containing low-grade copper sulfide. The culture was maintained for sixty days and then transferred to fresh medium. This process was repeated three more times and a final consortium exhibiting a copper extraction rate of 89.3% was obtained. RFLP and microarrays analysis of 16S rRNA sequences retrieved from the consortia showed that Acidithiobacilluscaldus, Leptospirillumferriphilum, Sulfobacillus sp., Acidiphilium sp., and Sulfolobus spp. were represented in higher numbers in the consortia obtained in the copper-containing medium than in the original consortium. In contrast, a decrease in Acidithiobacillus ferrooxidans, Alicyclobacillus sp., Pseudomonas sp., and Sulfobacillus thermosulfidooxidans was observed. The abundance of genes related to sulfur metabolism from At. caldus and Sulfolobus spp., iron oxidation from Leptospirillum sp. and metal resistance from most of the detected microorganisms increased as the consortium was successively transferred into fresh medium., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Acidithiobacillus thiooxidans A01 was added to a consortium of bioleaching bacteria including Acidithiobacilluscaldus, Leptospirillumferriphilum, Acidithiobacillus ferrooxidans, Sulfobacillus thermosulfidooxidans, Acidiphilium spp., and Ferroplasma thermophilum cultured in modified 9 K medium containing 0.5% (w/v) pyrite, and 10.7% increase of bioleaching rate was observed. Changes in community structure and gene expression were monitored with real-time PCR and functional gene arrays (FGAs). Real-time PCR showed that addition of At. thiooxidans caused increased numbers of all consortium members except At. caldus, and At. caldus, L. ferriphilum, and F. thermophilum remained dominant in this community. FGAs results showed that after addition of At. thiooxidans, most genes involved in iron, sulfur, carbon, and nitrogen metabolisms, metal resistance, electron transport, and extracellular polymeric substances of L. ferriphilum, F. thermophilum, and Acidiphilium spp., were up-regulated while most of these genes were down-regulated at 70-78 h in At. caldus and up-regulated in At. ferrooxidans, then down-regulated at 82-86 h., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Although nitrite effect on enhanced biological phosphorus removal (EBPR) has been previously studied, very limited research has been undertaken about the effect of nitrite accumulation caused by nitritation on EBPR. This paper focused on nitrite effect from nitritation on EBPR in a sequencing batch reactor treating domestic wastewater. Results showed that nitrite of below 10mg/L did not inhibit P-uptake and release; whereas EBPR deterioration was observed when nitrite accumulation reached 20mg/L. Due to P-uptake prior to nitritation, nitrite of 20mg/L has no effect on aerobic P-uptake. The main reason leading to EBPR deterioration was the competition of carbon source. Batch tests were conducted to investigate nitrite effect on anaerobic P-release. Under sufficient carbon source, nitrite of 30 mg/L had no impact on poly-β-hydroxyalkanoate (PHA) storage; contrarily, under insufficient carbon source, denitrifiers competing for carbon source with phosphorus accumulating organisms resulted in decrease of PHA synthesis and P-release., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

An assessment of seed quality on erythromycin production by recombinant strain Saccharopolyspora erythraea ZL1004 was investigated in 15 l fermenter. Adding 10 g/l corn steep liquor and 30 g/l soybean flour in seed medium were beneficial to improve cell growth, and the maximal biomass reached 36% at 40 h. Enzyme activity in cell showed that the maximal protease and minimum amylase were appeared in this stage. Compared with the control in 50 l fermenter, the cell metabolism with inoculation of the optimized seed cultivation was obviously quicker, and physiological response such as oxygen uptake rate (OUR) and carbon dioxide evolution rate (CER) were also improved. The maximal erythromycin A production was 9160 U/ml at 215 h, which was increased by 21.63% with respect to the control. It was the first report to integrate cell growth characteristics and physiological response method to assess the seed quality for erythromycin production., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

In a continuous anaerobic-anoxic-aerobic (A(2)O) process treating domestic wastewater at ambient temperatures, nitritation was achieved through a combination of short aerobic actual hydraulic retention time (AHRT) and low dissolved oxygen (DO) levels (0.3-0.5mg/L). The nitrite accumulation rate was about 90% and ammonia removal efficiency was over 95%. With respect to total nitrogen removal, nitritation-denitritation at low DO levels of 0.3-0.5mg/L was essentially equal to the complete nitrification-denitrification at DO levels of 1.5-2.5mg/L with the addition of external carbon sources. Regardless of low DO operation, sludge bulking did not occur since the sludge volume index was below 150ml/g. Real-time PCR assays showed that in response to complete and partial nitrification modes, the numbers of ammonia oxidizing bacteria population were 5.28x10(9)cells/g MLVSS and 3.95x10(10)cells/g MLVSS, respectively. Achievement of nitritation-denitritation is highly beneficial to the treatment of domestic wastewater in terms of lower carbon requirements and reduced aeration costs., (Copyright 2010. Published by Elsevier Ltd.)