NAD-Independent L-Lactate Dehydrogenase Is Required for L-Lactate Utilization in Pseudomonas stutzeri SDM

BACKGROUND: Various Pseudomonas strains can use L-lactate as their sole carbon source for growth. However, the L-lactate-utilizing enzymes in Pseudomonas have never been identified and further studied. METHODOLOGY/PRINCIPAL FINDINGS: An NAD-independent L-lactate dehydrogenase (L-iLDH) was purified from the membrane fraction of Pseudomonas stutzeri SDM. The enzyme catalyzes the oxidation of L-lactate to pyruvate by using FMN as cofactor. After cloning its encoding gene (lldD), L-iLDH was successfully expressed, purified from a recombinant Escherichia coli strain, and characterized. An lldD mutant of P. stutzeri SDM was constructed by gene knockout technology. This mutant was unable to grow on L-lactate, but retained the ability to grow on pyruvate. CONCLUSIONS/SIGNIFICANCE: It is proposed that L-iLDH plays an indispensable function in Pseudomonas L-lactate utilization by catalyzing the conversion of L-lactate into pyruvate

Techno-economic comparative assessment of novel lignin depolymerization routes to bio-based aromatics

This paper presents a techno-economic assessment of three novel routes for the production of bio-based aromatics from lignin. It aims to provide insights into their feasibility and hotspots at an early stage of development to guide further research and development and to facilitate commercialization. The lignin conversion routes are: (non-catalytic) lignin pyrolysis, direct hydrodeoxygenation (HDO), and hydrothermal upgrading (HyThUp). The products generated are mixed oxygenated aromatic monomers (MOAMON), light organics, heavy organics, and char. For the technical assessment, conceptual design followed by process modeling in Aspen Plus was based on experimental yields. The models generated indispensable data on material and energy flows. An economic assessment was then conducted by estimating operating and capital costs. Return on investment (ROI), payback period (PBP), and net present value (NPV) were used as key performance indicators. Downstream processing was especially demanding in the HyThUp process due to the presence of a significant flow rate of water in the system, which significantly increased external utility requirements. Due to complex separations, the HyThUp process showed the highest capital cost (35% more than pyrolysis). Operating costs were the highest for the direct HDO process (34% more than pyrolysis) due to the use of hydrogen. Overall, the direct HDO process showed the highest ROI (12%) and the shortest PBP (5 years) due to high yields of valuable heavy organics (32%) and MOAMON (24%). Direct HDO was found to be feasible with a positive NPV based on prices used in the assessment. Among the three processes investigated, the direct HDO process therefore appeared to be the most promising, and consideration should be given to further development and commercialization of this process.Energy & Industr

Control and imaging of O(1D2) precession

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