Boosting d -lactate production in engineered cyanobacteria using sterilized anaerobic digestion effluents

Hollinshead, Whitney D.; Varman, Arul M.; You, Le; Hembree, Zachary; Tang, Yinjie J.

doi:10.1016/j.biortech.2014.07.003

Cited by 30 publications

(18 citation statements)

References 28 publications

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“…The cathode was filled with 220 mL of synthetic wastewater as "artificial AD effluent", which was prepared with the same buffer solution containing varying concentrations of sodium acetate, sodium propionate and sodium butyrate (total VFAs ranges from 0 to 120 mM). To mimic real AD effluent, we set the concentration ratio of acetate, propionate and butyrate in "artificial AD effluent" at 5:1:1 which corresponds well to what is often measured in biogas plants (Hollinshead et al, 2014). In one set of tests, we tested the sensor with voltages at 0.3, 0.5, 0.8 and 1.0 V to elucidate the effect of external voltage on the current generation.…”

Section: Biosensor Setup and Operationmentioning

confidence: 99%

Bio-electrolytic sensor for rapid monitoring of volatile fatty acids in anaerobic digestion process

Jin

Zhao

et al. 2017

Water Research

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This study presents an innovative biosensor that was developed on the basis of a microbial electrolysis cell for fast and reliable measurement of volatile fatty acids (VFA) during anaerobic digestion (AD) process. The bio-electrolytic sensor was first tested with synthetic wastewater containing varying concentrations of VFA. A linear correlation (R = 0.99) between current densities (0.03 ± 0.01 to 2.43 ± 0.12 A/m) and VFA concentrations (5-100 mM) was found. The sensor performance was then investigated under different affecting parameters such as the external voltage, VFA composition ratio, and ionic strength. Linear relationship between the current density and VFA concentrations was always observed. Furthermore, the bio-electrolytic sensor proved ability to handle interruptions such as the presence of complex organic matter, anode exposure to oxygen and low pH. Finally, the sensor was applied to monitor VFA concentrations in a lab-scale AD reactor for a month. The VFA measurements from the sensor correlated well with those from GC analysis which proved the accuracy of the system. Since hydrogen was produced in the cathode as byproduct during monitoring, the system could be energy self-sufficient. Considering the high accuracy, short response time, long-term stability and additional benefit of H production, this bio-electrolytic sensor could be a simple and cost-effective method for VFA monitoring during AD and other anaerobic processes.

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Section: Biosensor Setup and Operationmentioning

confidence: 99%

Bio-electrolytic sensor for rapid monitoring of volatile fatty acids in anaerobic digestion process

Jin

Zhao

et al. 2017

Water Research

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“…Phototrophs harness light for their energy needs, making them a more sustainable biotechnology platform than heterotrophs, which must be supplied with a source of reduced carbon (Berla et al, 2013;Ducat et al, 2011). Cyanobacteria are fast-growing phototrophs (Yokoo et al, 2015) that can live in conditions that do not support the growth of crops; thus, they do not compete for arable land (Hollinshead et al, 2014;Pade and Hagemann, 2015). The model cyanobacterium, Synechocystis sp.…”

Section: Introductionmentioning

confidence: 99%

Physical, chemical, and metabolic state sensors expand the synthetic biology toolbox for Synechocystis sp. PCC 6803

Immethun

DeLorenzo

Focht

et al. 2017

Biotech & Bioengineering

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Many under-developed organisms possess important traits that can boost the effectiveness and sustainability of microbial biotechnology. Photoautotrophic cyanobacteria can utilize the energy captured from light to fix carbon dioxide for their metabolic needs while living in environments not suited for growing crops. Various value-added compounds have been produced by cyanobacteria in the laboratory; yet, the products' titers and yields are often not industrially relevant and lag behind what have been accomplished in heterotrophic microbes. Genetic tools for biological process control are needed to take advantage of cyanobacteria's beneficial qualities, as tool development also lags behind what has been created in common heterotrophic hosts. To address this problem, we developed a suite of sensors that regulate transcription in the model cyanobacterium Synechocystis sp. PCC 6803 in response to metabolically relevant signals, including light and the cell's nitrogen status, and a family of sensors that respond to the inexpensive chemical, l-arabinose. Increasing the number of available tools enables more complex and precise control of gene expression. Expanding the synthetic biology toolbox for this cyanobacterium also improves our ability to utilize this important under-developed organism in biotechnology. Biotechnol. Bioeng. 2017;114: 1561-1569. © 2017 Wiley Periodicals, Inc.

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“…As shown in Table S4 , both Hollinshead et al . 14 and Varman et al . 17 have reported the enhanced d -lactate production using Synechocystis sp.…”

Section: Discussionmentioning

confidence: 94%

“…Biosynthesis of d -lactate from CO 2 has been achieved and is characterized in cyanobacteria, such as Synechocystis sp. PCC6803, through genetic engineering 11 12 13 14 15 16 17 18 32 . As shown in Table S4 , both Hollinshead et al .…”

Section: Discussionmentioning

confidence: 99%

“…As lactate biosynthesis in cyanobacteria is attractive, several studies have investigated lactate production in cyanobacteria 11 12 13 14 15 16 17 18 . However, engineering of cyanobacteria for d -lactate production is limited by relatively low productivity, although efforts have been made to enhance its biosynthesis through both genetic engineering and optimization of culture conditions 14 16 17 . Low productivity may be attributed to cofactor imbalance (insufficient supply of NADH), because cyanobacteria produce NADPH as the major carrier of reducing equivalents 19 .…”

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confidence: 99%

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Enhancing the light-driven production of d-lactate by engineering cyanobacterium using a combinational strategy

Tao

et al. 2015

Sci Rep

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It is increasingly attractive to engineer cyanobacteria for bulk production of chemicals from CO2. However, cofactor bias of cyanobacteria is different from bacteria that prefer NADH, which hampers cyanobacterial strain engineering. In this study, the key enzyme d-lactate dehydrogenase (LdhD) from Lactobacillus bulgaricus ATCC11842 was engineered to reverse its favored cofactor from NADH to NADPH. Then, the engineered enzyme was introduced into Synechococcus elongatus PCC7942 to construct an efficient light-driven system that produces d-lactic acid from CO2. Mutation of LdhD drove a fundamental shift in cofactor preference towards NADPH, and increased d-lactate productivity by over 3.6-fold. We further demonstrated that introduction of a lactic acid transporter and bubbling CO2-enriched air also enhanced d-lactate productivity. Using this combinational strategy, increased d-lactate concentration and productivity were achieved. The present strategy may also be used to engineer cyanobacteria for producing other useful chemicals.

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Boosting d -lactate production in engineered cyanobacteria using sterilized anaerobic digestion effluents

Cited by 30 publications

References 28 publications

Bio-electrolytic sensor for rapid monitoring of volatile fatty acids in anaerobic digestion process

Bio-electrolytic sensor for rapid monitoring of volatile fatty acids in anaerobic digestion process

Physical, chemical, and metabolic state sensors expand the synthetic biology toolbox for Synechocystis sp. PCC 6803

Enhancing the light-driven production of d-lactate by engineering cyanobacterium using a combinational strategy

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