Improving β-glucosidase and xylanase production in a combination of waste substrate from domestic wastewater treatment system and agriculture residues.
Liang Cuiyi,Xu Zihan,Wang Qiong,Wang Wen,Xu Huijuan,Guo Ying,Qi Wei,Wang Zhongming
Bioresource technology
Cellulase and hemicellulase activities are considered to the major bottlenecks in the lignocellulosic biorefinery process, especially in an enzyme cocktail lacking β-glucosidase (BGL) and xylanase (XYL). In view of this issue, higher levels of BGL and XYL activities were obtained in the presence of wastewater and activated sludge as an induction medium mixed with 5% of rice straw by Hypocrea sp. W. The analysis of the ionic content showed that a relatively low sludge dose could enhance the production of BGL and XYL. Most importantly, compared to a medium using freshwater, the proportion of 1:10 sludge to wastewater, which contained nutrient elements, led to 3.4-fold BGL and 3.7-fold XYL production improvements. This research describes the reuse of substrates that are largely and continuously generated from domestic wastewater treatment systems and agriculture residues, which consequently leads to the development of a simultaneous enzyme production process for sustainable biorefinery practices.
10.1016/j.biortech.2020.124019
Insight into the effects and biotechnological production of kestoses, the smallest fructooligosaccharides.
Ni Dawei,Xu Wei,Zhu Yingying,Pang Xiaoyang,Lv Jiaping,Mu Wanmeng
Critical reviews in biotechnology
Kestoses, the smallest fructooligosaccharides, are trisaccharides composed of a fructose molecule and a sucrose molecule linked by either -(2,1) or -(2,6) linkage. 1-kestose, 6-kestose and neokestose are the three types of kestoses occurring in nature. As the main kind of fructooligosaccharide, kestoses share similar physiological effects with other fructooligosaccharides, and they have recently been determined to show more notable effects in promoting the growth of probiotics including and than those of other fructooligosaccharides. Kestoses exist in many plants, but the relatively low content and the isolation and purification are the main barriers limiting their industrial application. The production of kestoses by enzymatic biosynthesis and microbial fermentation has the potential to facilitate its production and industrial use. In this article, the recent advances in the research of kestoses were overviewed, including those studying their functions and production. Kestose-producing enzymes were introduced in detail, and microbial production and fermentation optimization techniques for enhancing the yield of kestoses were addressed. -Fructofuranosidase is the main one used to produce kestoses because of the extensive range of microbial sources. Therefore, the production of kestoses by microorganisms containing -fructofuranosidase has also been reviewed. However, few molecular modification studies have attempted to change the production profile of some enzymes and improve the yield of kestoses, which is a topic that should garner more attention. Additionally, the production of kestoses using food-grade microorganisms may be beneficial to their application in the food industry.
10.1080/07388551.2020.1844622
Optimization of process parameters for determination of trace Hazardous dyes from industrial wastewaters based on nanostructures materials under ultrasound energy.
Alipanahpour Dil Ebrahim,Ghaedi Mehrorang,Asfaram Arash,Mehrabi Fatemeh,Bazrafshan Ali Akbar
Ultrasonics sonochemistry
In this study, ultrasound-assisted dispersive solid phase micro-extraction based on nanosorbent namely silver-zinc oxide nanoparticles loaded on activated carbon (Ag-ZnO-NP-AC) combined with derivative spectrophotometry method for the simultaneous pre-concentration and determination of Methyl Green (MG) and Rose Bengal (RB) dyes in water and industrial wastewater. Characterized sorbent by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), particle-size distribution (PSD), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and Transmission electron microscopy (TEM) analysis with superior adsorption capacity was applied in ultrasound assisted dispersive-solid-phase micro-extraction (UA-DSPME) methodology. pH, sorbent mass, ultrasonication time, and eluent volume influence and contribution on response correspond to simultaneous pre-concentration and determination of MG and RB were optimized by response surface methodology (RSM) and results were compared with the experimental values. Under the optimal conditions (UA-DSPME), the enrichment factors (EFs) were 93.89 and 97.33 for the MG and RB dyes, respectively. The limits of detection were 2.14 and 2.73ngmL and the limit of quantification were 7.15 and 9.09ngmL for MG and RB, respectively. The analytes can be determined over 10-2000ngmL with recoveries between 90.8% to 97.7% and RSDs less than 3.6%. The developed method due to simplicity and rapidity is able successful for repeatable and accurate monitoring of under study analytes from complicated matrices.
10.1016/j.ultsonch.2017.07.022
Optimization of process parameters for hydrothermal conversion of castor residue.
Kaur Ravneeet,Gera Poonam,Jha Mithilesh Kumar,Bhaskar Thallada
The Science of the total environment
Castor plant (Ricinus communis) is a fast-growing shrub from Euphorbiaceae family. India ranks first in the world for the production of castor seeds. The generation of residue from its leaves and stems is more than 50% of the whole plant. This research work involves the estimation of the optimum condition for the production/value addition by hydrothermal liquefaction of castor residue using factorial design. Temperature (T) and residence time (RT) are the key parameters that affect the bio-oil yield. A 3 full factorial design was employed to understand the affects the bio-oil yield and conversion with key parameters. The key parameter and its interaction effects were analyzed by analysis of variance (ANOVA); F-test and p-values were used to rank the process variable affecting the total bio-oil yield. It was observed that the temperature imparts significant effect on total bio-oil yield. The optimum conditions to obtain maximum total bio-oil yield are T = 300 °C and RT = 60 min. The statistical model was best fitted with high coefficient of determination (R) of 0.9994 and 0.9473 for total bio-oil yield and conversion respectively.
10.1016/j.scitotenv.2019.05.430
Biosynthesis of 2,5-furan dicarboxylic acid by Aspergillus flavus APLS-1: Process optimization and intermediate product analysis.
Rajesh Rajendran Omana,Godan Tharangattumana Krishnan,Rai Amit Kumar,Sahoo Dinabandhu,Pandey Ashok,Binod Parameswaran
Bioresource technology
The aim of the present study was to develop an eco-friendly biological process for the production of 2,5-furan dicarboxylic acid (FDCA) from 5-hydroxy methylfurfuraldehyde (HMF) using microorganisms. Microorganisms were isolated from the soil samples and evaluated for its biotransformation efficiency. Among the isolates, Aspergillus flavus APLS-1 was found to be potent for efficient conversion of HMF to FDCA. The bioconversion parameters were optimized by Box-Behnken design. The optimization resulted in 67% conversion efficiency where 1 g/L HMF (8 mM) was transformed to 0.83 g/L (6.6 mM) FDCA in 14 days at pH6.5 with biomass size of 5.7 g/L and biomass age 60 h. This is the first report on Aspergillus sp., capable of detoxifying HMF and produces FDCA.
10.1016/j.biortech.2019.03.105
Synthetic dyes biodegradation by fungal ligninolytic enzymes: Process optimization, metabolites evaluation and toxicity assessment.
Sosa-Martínez Jazel Doménica,Balagurusamy Nagamani,Montañez Julio,Peralta Rosely Aparecida,Moreira Regina de Fátima Peralta Muniz,Bracht Adelar,Peralta Rosane Marina,Morales-Oyervides Lourdes
Journal of hazardous materials
This work aimed to provide information that contributes to establishing environmental-friendly methods for synthetic dyes' degradation. The potential decolorization capacity of the crude enzymatic extract produced by Phanerochaete chrysosporium CDBB 686 using corncob as a substrate was evaluated on seven different dyes. Critical variables affecting the in-vitro decolorization process were further evaluated and results were compared with an in-vivo decolorization system. Decolorization with enzymatic extracts presented advantages over the in-vivo system (higher or similar decolorization within a shorter period). Under improved in-vitro process conditions, the dyes with higher decolorization were: Congo red (41.84 %), Poly R-478 (56.86 %), Methyl green (69.79 %). Attempts were made to confirm the transformation of the dyes after the in-vitro process as well as to establish a molecular basis for interpreting changes in toxicity along with the degradation process. In-vitro degradation products of Methyl green presented a toxicity reduction compared with the original dye; however, increased toxicity was found for Congo red degradation products when compared with the original dyes. Thus, for future applications, it is crucial to evaluate the mechanisms of biodegradation of each target synthetic dye as well as the toxicity of the products obtained after enzymatic oxidation.
10.1016/j.jhazmat.2020.123254
Experimental optimization and techno-economic analysis of bioethanol production by simultaneous saccharification and fermentation process using sugarcane straw.
Pratto Bruna,Dos Santos-Rocha Martha Suzana Rodrigues,Longati Andreza Aparecida,de Sousa Júnior Ruy,Cruz Antonio José Gonçalves
Bioresource technology
The present work aims to determine a suitable yield-productivity balance in bioethanol production from hydrothermally pretreated sugarcane straw via pre-saccharification (PS) and simultaneous saccharification and fermentation (SSF). PS experiments were carried out evaluating effects of enzymatic dosage, biomass loading, and PS time. The performance of the whole process (PSSSF) was evaluated based on overall ethanol yield and productivity considering a simultaneous optimization (desirability function) of both variables. The multi-criteria optimization enabled to reach 5.7% w/w ethanol concentration yielding 290 L of ethanol per ton of pretreated sugarcane straw within 45 h of total processing time. Furthermore, a techno-economic analysis was performed under optimized conditions (14.5 FPU/g, 19.3% w/v biomass loading and 33 h PS time). This process was integrated into a first-generation plant. Although the economic evaluation exhibited a negative performance, a sensitivity analysis indicated that a decrease of 23.3% in operational expenditure would be enough to achieve feasibility.
10.1016/j.biortech.2019.122494
Process optimization of fucoxanthin production with Tisochrysis lutea.
Gao Fengzheng,Teles Cabanelas Itd Iago,Wijffels René H,Barbosa Maria J
Bioresource technology
To optimize fucoxanthin production in Tisochrysis lutea, the effect of different process parameters on fucoxanthin productivity (Pfx) were evaluated using batch and continuous experiments. In batch, the highest Pfx was found at 30 °C and 300 μmol m s, allowing to design continuous experiments to optimize the dilution rate. The highest ever reported Pfx (9.43-9.81 mg L d) was achieved at dilution rates of 0.53 and 0.80 d. Irradiance was varied (50-500 μmol m s) to result in a range of absorbed light between 2.23 and 25.80 mol m d at a fixed dilution rate (0.53 d). These experiments validated the hypothesis that light absorbed can be used to predict fucoxanthin content, resulting in 2.23 mol m d triggering the highest fucoxanthin content (16.39 mg/g). The highest Pfx was found with 18.38 mol m d. These results can be used to achieve high Pfx or fucoxanthin content during cultivation of Tisochrysis lutea.
10.1016/j.biortech.2020.123894
Combining metabolic engineering and process optimization to improve production and secretion of fatty acids.
Ledesma-Amaro Rodrigo,Dulermo Remi,Niehus Xochitl,Nicaud Jean-Marc
Metabolic engineering
Microbial oils are sustainable alternatives to petroleum for the production of chemicals and fuels. Oleaginous yeasts are promising source of oils and Yarrowia lipolytica is the most studied and engineered one. Nonetheless the commercial production of biolipids is so far limited to high value products due to the elevated production and extraction costs. In order to contribute to overcoming these limitations we exploited the possibility of secreting lipids to the culture broth, uncoupling production and biomass formation and facilitating the extraction. We therefore considered two synthetic approaches, Strategy I where fatty acids are produced by enhancing the flux through neutral lipid formation, as typically occurs in eukaryotic systems and Strategy II where the bacterial system to produce free fatty acids is mimicked. The engineered strains, in a coupled fermentation and extraction process using alkanes, secreted the highest titer of lipids described so far, with a content of 120% of DCW.
10.1016/j.ymben.2016.06.004
Low-temperature thermal pre-treatment of municipal wastewater sludge: Process optimization and effects on solubilization and anaerobic degradation.
Nazari Laleh,Yuan Zhongshun,Santoro Domenico,Sarathy Siva,Ho Dang,Batstone Damien,Xu Chunbao Charles,Ray Madhumita B
Water research
The present study examines the relationship between the degree of solubilization and biodegradability of wastewater sludge in anaerobic digestion as a result of low-temperature thermal pre-treatment. The main effect of thermal pre-treatment is the disintegration of cell membranes and thus solubilization of organic compounds. There is an established correlation between chemical oxygen demand (COD) solubilization and temperature of thermal pre-treatment, but results of thermal pre-treatment in terms of biodegradability are not well understood. Aiming to determine the impact of low temperature treatments on biogas production, the thermal pre-treatment process was first optimized based on an experimental design study on waste activated sludge in batch mode. The optimum temperature, reaction time and pH of the process were determined to be 80 °C, 5 h and pH 10, respectively. All three factors had a strong individual effect (p < 0.001), with a significant interaction effect for temp. pH (p = 0.002). Thermal pre-treatments, carried out on seven different municipal wastewater sludges at the above optimum operating conditions, produced increased COD solubilization of 18.3 ± 7.5% and VSS reduction of 27.7 ± 12.3% compared to the untreated sludges. The solubilization of proteins was significantly higher than carbohydrates. Methane produced in biochemical methane potential (BMP) tests, indicated initial higher rates (p = 0.0013) for the thermally treated samples (k up to 5 times higher), although the ultimate methane yields were not significantly affected by the treatment.
10.1016/j.watres.2016.11.055
Resource-Saving Production of Dialdehyde Cellulose: Optimization of the Process at High Pulp Consistency.
ChemSusChem
Oxidation of cellulose with periodate under aqueous conditions yields dialdehyde cellulose, a promising functional cellulose derivative. The main obstacles for this oxidation have been its slow kinetics and the dilute reaction conditions, requiring considerable amounts of water and energy. In this study, these drawbacks are overcome by conducting the oxidation at high cellulosic pulp consistency with a cellulose/water weight ratio of 1:4. The oxidizer, cellulose, and water are efficiently mixed in a ball mill. Oxidation occurs mostly in the subsequent step, during the resting time (no further milling/mixing is required). The reaction and resource efficiency of the process are optimized by experimental design and a maximum aldehyde content of 8 mmol g is obtained with a periodate/cellulose molar ratio of 1.25, a milling time of 2 min, and a resting time of 8 h. The developed method allows fine tuning of the oxidation level and is a key step towards the sustainable periodate oxidation of cellulose also on larger scale.
10.1002/cssc.201901885
Iodate and nitrate transformation by Agrobacterium/Rhizobium related strain DVZ35 isolated from contaminated Hanford groundwater.
Lee Brady D,Ellis Joshua T,Dodwell Alex,Eisenhauer Emalee E R,Saunders Danielle L,Lee M Hope
Journal of hazardous materials
Nitrate and radioiodine (I) contamination is widespread in groundwater underneath the Central Plateau of the Hanford Site. I, a byproduct of nuclear fission, is of concern due to a 15.7 million year half-life, and toxicity. The Hanford 200 West Area contains plumes covering 4.3 km with average I concentrations of 3.5 pCi/L. Iodate accounts for 70.6% of the iodine present and organo-iodine and iodide make up 25.8% and 3.6%, respectively. Nitrate plumes encompassing the I plumes have a surface area of 16 km averaging 130 mg/L. A nitrate and iodate reducing bacterium closely related to Agrobacterium, strain DVZ35, was isolated from sediment incubated in a I plume. Iodate removal efficiency was 36.3% in transition cultures, and 47.8% in anaerobic cultures. Nitrate (10 mM) was also reduced in the microcosm. When nitrate was spiked into the microcosms, iodate removal efficiency was 84.0% and 69.2% in transition and anaerobic cultures, respectively. Iodate reduction was lacking when nitrate was absent from the growth medium. These data indicate there is simultaneous reduction of nitrate and iodate by DVZ35, and iodate is reduced to iodide. Results provide the scientific basis for combined nitrogen and iodine cycling throughout the Hanford Site.
10.1016/j.jhazmat.2018.02.006
Engineering synergetic CO-fixing pathways for malate production.
Hu Guipeng,Zhou Jie,Chen Xiulai,Qian Yuanyuan,Gao Cong,Guo Liang,Xu Peng,Chen Wei,Chen Jian,Li Yin,Liu Liming
Metabolic engineering
Increasing the microbial CO-fixing efficiency often requires supplying sufficient ATP and redirecting carbon flux for the production of metabolites. However, addressing these two issues concurrently remains a challenge. Here, we present a combinational strategy based on a synergetic CO-fixing pathway that combines an ATP-generating carboxylation reaction in the central metabolic pathway with the ATP-consuming RuBisCO shunt in the carbon fixation pathway. This strategy provides enough ATP to improve the efficiency of CO fixation and simultaneously rewires the CO-fixing pathway to the central metabolic pathway for the biosynthesis of chemicals. We demonstrate the application of this strategy by increasing the CO-fixing rate and malate production in the autotroph Synechococcus elongatus by 110% and to 260 μM respectively, as well as increasing these two factors in the heterotrophic CO-fixing Escherichia coli by 870% and to 387 mM respectively.
10.1016/j.ymben.2018.05.007
Engineering the production of dipicolinic acid in E. coli.
McClintock Maria K,Fahnhorst Grant W,Hoye Thomas R,Zhang Kechun
Metabolic engineering
Dicarboxylic acids, such as the phthalic acids and their derivatives, are monomeric components in several important polyesters and polyamides. In most cases, these compounds are derived from fossil fuels and are not easily biodegradable. Dipicolinic acid (DPA) is a biologically derived aromatic di-acid that has a similar structure to isophthalic acid. Furthermore, DPA has been shown to give rise to polyesters, is readily biodegradable, and is non-toxic. DPA is naturally produced by Bacillus and Clostridium species during sporulation and can comprise up to 15% of the dry weight of bacterial spores. In this paper we demonstrate the first heterologous production of DPA and identify the genes appropriate for gram-scale production in the industrial workhorse organism, E. coli. Initially, several combinations of genes from the lysine pathway, including lysC, asd, dapA, and dapB, were overexpressed to determine which genes are necessary for recombinant production in E. coli. The in vitro activity of dipicolinate synthase was then compared between Bacillus subtilis and Clostridium perfringens. Next, in order to improve DPA production from glucose, an optimized strain was created that lacked several genes (lysA, tdh, and metA), resulting in 5.21 g/L DPA when 5 g/L of aspartate was supplied. Then, several aspartate kinases and dipicolinate synthases were screened for optimal activity in E. coli. The optimal genes were combined with the overexpression of phosphoenolpyruvate carboxylase to develop a full biosynthetic pathway capable of producing a titer of 4.7 g/L DPA directly from glucose. In summary, we have performed a detailed biochemical study of the key pathway enzyme dipicolinate synthase and achieved scalable heterogeneous production of DPA in the workhorse organism E. coli.
10.1016/j.ymben.2018.05.009
Exploring biochemical pathways for mono-ethylene glycol (MEG) synthesis from synthesis gas.
Islam M Ahsanul,Hadadi Noushin,Ataman Meric,Hatzimanikatis Vassily,Stephanopoulos Gregory
Metabolic engineering
Mono-ethylene glycol (MEG) is an important petrochemical with widespread use in numerous consumer products. The current industrial MEG-production process relies on non-renewable fossil fuel-based feedstocks, such as petroleum, natural gas, and naphtha; hence, it is useful to explore alternative routes of MEG-synthesis from gases as they might provide a greener and more sustainable alternative to the current production methods. Technologies of synthetic biology and metabolic engineering of microorganisms can be deployed for the expression of new biochemical pathways for MEG-synthesis from gases, provided that such promising alternative routes are first identified. We used the BNICE.ch algorithm to develop novel and previously unknown biological pathways to MEG from synthesis gas by leveraging the Wood-Ljungdahl pathway of carbon fixation of acetogenic bacteria. We developed a set of useful pathway pruning and analysis criteria to systematically assess thousands of pathways generated by BNICE.ch. Published genome-scale models of Moorella thermoacetica and Clostridium ljungdahlii were used to perform the pathway yield calculations and in-depth analyses of seven (7) newly developed biological MEG-producing pathways from gases, including CO, CO, and H. These analyses helped identify not only better candidate pathways, but also superior chassis organisms that can be used for metabolic engineering of the candidate pathways. The pathway generation, pruning, and detailed analysis procedures described in this study can also be used to develop biochemical pathways for other commodity chemicals from gaseous substrates.
10.1016/j.ymben.2017.04.005
Enhancing candicidin biosynthesis by medium optimization and pH stepwise control strategy with process metabolomics analysis of Streptomyces ZYJ-6.
Liu Xiaoyun,Sun Xiaojuan,Wang Tong,Zhang Xin,Tian Xiwei,Zhuang Yingping,Chu Ju
Bioprocess and biosystems engineering
Candicidin is one of the most effective antimonilial agents. In order to enhance candicidin productivity, medium optimization and pH stepwise control strategy in process optimization were conducted by Streptomyces ZYJ-6. With the aid of Design Expert software and N/C/P-sources regulation, chemically defined medium fit for cell growth and candicidin biosynthesis was developed. Moreover, pH effects on cell growth and metabolism were investigated. The results indicated that the optimal pH for cell growth and candicidin biosynthesis were 6.8 and 7.8, respectively. The metabolomics analysis revealed that the pH stepwise control strategy (pH 6.8-7.8) combined the advantages of pH 6.8 and pH 7.8 and avoided precursor limitation in pH 6.8 and 7.8. Consequently, the pH stepwise control strategy played positive performance on cell growth and candicidin biosynthesis with the maximum titer of 5161 µg/mL. The titer of 5161 µg/mL was the highest level ever reported for candicidin production, which laid a solid foundation for industrial application. Additionally, pH stepwise control strategy was important reference for process optimization.
10.1007/s00449-018-1997-x
Electro-fermentation and redox mediators enhance glucose conversion into butyric acid with mixed microbial cultures.
Paiano Paola,Menini Miriam,Zeppilli Marco,Majone Mauro,Villano Marianna
Bioelectrochemistry (Amsterdam, Netherlands)
Electro-fermentation (EF) is an emerging and promising technology consisting in the use of a polarized electrode to control the spectrum of products deriving from anaerobic bioprocesses. Here, the effect of electrode polarization on the fermentation of glucose has been studied with two mixed microbial cultures, both in the absence and in the presence of exogenous redox mediators, to verify the viability of the proposed approach under a broader and previously unexplored range of operating conditions. In unmediated experiments, EF (with the cathode polarized at -700 mV vs. SHE, Standard Hydrogen Electrode) caused an increase in the yield of butyric acid production provided that glucose was consumed along with its own fermentation products (i.e. acetic acid and ethanol). The maximum obtained yield accounted for 0.60 mol mol. Mediated experiments were performed with Neutral Red or AQDS at a concentration of 500 μM both in the absence and in the presence of the electrode polarized at -700 mV or -300 mV vs. SHE, respectively. Mediators showed a high selectivity towards the generation of n-butyric acid isomer from the condensation of acetate and ethanol, hence suggesting that they provided microbial cells with the required reducing power otherwise deriving from glucose in unmediated experiments.
10.1016/j.bioelechem.2019.107333
Efficient production of short-chain fatty acids from anaerobic fermentation of liquor wastewater and waste activated sludge by breaking the restrictions of low bioavailable substrates and microbial activity.
Luo Jingyang,Wu Jing,Zhang Qin,Feng Qian,Wu Lijuan,Cao Jiashun,Li Chao,Fang Fang
Bioresource technology
An efficient approach of bioconverting the organic wastes in liquor wastewater (LW) and waste activated sludge (WAS) to valuable short-chain fatty acids (SCFAs) via anaerobic fermentation was explored. The maximal SCFAs concentration was 5400 mg COD/L with approximate 80.0% acetic and propionic acids under optimized conditions (LW/WAS ratio 1:1, pH 8 and fermentation 4 d). Mechanisms investigation found that the fermentation of LW/WAS made up the drawbacks of sole WAS fermentation by improving the bioavailable substrates and low C/N ratio to stimulate the microbial activities. The bioconversion efficiency of substrates for SCFAs generation was therefore enhanced. The humic acids present in LW could also play positive roles in SCFAs promotion. Moreover, the performance of LW/WAS fermentation was highly correlated with appropriate fermentation pH. The fermentative bacteria responsible for SCFAs production were highly enriched and the activities of key hydrolases, acid-forming enzymes and ATP concentration were greatly improved at pH 8.
10.1016/j.biortech.2018.08.039
Power generation and microbial community analysis in microbial fuel cells: A promising system to treat organic acid fermentation wastewater.
Xia Tian,Zhang Xueli,Wang Huimin,Zhang Yachao,Gao Yan,Bian Congcong,Wang Xia,Xu Ping
Bioresource technology
To explore a sustainable and efficient treatment approach for organic acid fermentation wastewater, two microbial fuel cells (MFCs) systems inoculated with wastewater or domesticated microbial community were constructed in this study. Compared with the MFC inoculated with domesticated microbial community, the MFC inoculated with wastewater not only showed higher power density (543.75 mW m) and coulomb efficiency (22.10%), but also exhibited higher removal rates of chemical oxygen demand (75.59%), total nitrogen (76.15%), and ammonia nitrogen (83.23%), meeting the demand of wastewater discharge standard of China. Sequencing analysis revealed that the MFC inoculated with wastewater were richer in microbial community, and some bacteria such as Saprospiraceae and Caldilineaceae were beneficial for its good performance. In contrast, the microbial community of the MFC inoculated with domesticated microbial community was relatively simple. These results indicated that MFCs may be a sustainable method for organic acid fermentation wastewater treatment without any preprocessing.
10.1016/j.biortech.2019.03.119
Metabolic engineering of Saccharomyces cerevisiae for the overproduction of short branched-chain fatty acids.
Yu Ai-Qun,Pratomo Juwono Nina Kurniasih,Foo Jee Loon,Leong Susanna Su Jan,Chang Matthew Wook
Metabolic engineering
Short branched-chain fatty acids (SBCFAs, C4-6) are versatile platform intermediates for the production of value-added products in the chemical industry. Currently, SBCFAs are mainly synthesized chemically, which can be costly and may cause environmental pollution. In order to develop an economical and environmentally friendly route for SBCFA production, we engineered Saccharomyces cerevisiae, a model eukaryotic microorganism of industrial significance, for the overproduction of SBCFAs. In particular, we employed a combinatorial metabolic engineering approach to optimize the native Ehrlich pathway in S. cerevisiae. First, chromosome-based combinatorial gene overexpression led to a 28.7-fold increase in the titer of SBCFAs. Second, deletion of key genes in competing pathways improved the production of SBCFAs to 387.4 mg/L, a 31.2-fold increase compared to the wild-type. Third, overexpression of the ATP-binding cassette (ABC) transporter PDR12 increased the secretion of SBCFAs. Taken together, we demonstrated that the combinatorial metabolic engineering approach used in this study effectively improved SBCFA biosynthesis in S. cerevisiae through the incorporation of a chromosome-based combinatorial gene overexpression strategy, elimination of genes in competitive pathways and overexpression of a native transporter. We envision that this strategy could also be applied to the production of other chemicals in S. cerevisiae and may be extended to other microbes for strain improvement.
10.1016/j.ymben.2015.12.005