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The enzymatic reduction of carbon dioxide presents limited applicability due to denaturation and the impossibility of biocatalyst recovery; disadvantages that can be minimized by its immobilization. Here, a recyclable bio-composed system was constructed by in-situ encapsulation under mild conditions using formate dehydrogenase in a ZIF-8 metalorganic framework (MOF) in the presence of magnetite. The partial dissolution of ZIF-8 in the enzyme's operation medium can be relatively inhibited if the concentration of magnetic support used exceeds 10 mg mL-1 . The bio-friendly environment for immobilization does not harm the integrity of the biocatalyst, and the production of formic acid is improved 3.4-fold compared to the free enzyme because the MOFs act as concentrators of the enzymatic cofactor. Furthermore, the bio-composed system retains 86 % of its activity after a long time of five cycles, thus indicating an excellent magnetic recovery and a good reusability.

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Abstract Background: Organic acids and ammonium salts added to drinking water can optimize productivity of broiler chickens. Objective: To evaluate the effect of acidifying drinking water on productive performance, blood and intestinal pH, and intestinal morphology of broilers. Methods: 1,400 one-day-old broiler chicks were used to evaluate two pH levels (4 and 6) of drinking water during three periods (1-21, 1-28, and 1-42 days of age). The treatments consisted of water added with a blend of formic acid (31%), propionic acid (19%), and their salts ammonium formate (26%), and ammonium propionate (6%) compared to a control group (pH 8). Results: Compared to the control, the groups consuming water at pH 6 (0.038 moles) continuously for 42 days improved (p≤0.01) live weight (2.785 vs 2.691 kg), feed conversion ratio (1.430 vs 1.463 kg/kg), and increased the number of intestinal villi (59.0 vs 55.7). Additionally, blood and intestinal pH was reduced vs the control group (7.75 vs 7.89; 6.32 vs 6.41, respectively). Conclusion: The blend of formic and propionic acids and their ammonium salts in drinking water at pH 6 during the complete production cycle of broilers improves performance, increases the number of intestinal villi, and reduces the pH of blood, duodenum, and ileum.

Resumen Antecedentes: Agregar ácidos orgánicos y sus sales amoniacales en el agua de bebida de pollos de engorde puede optimizar su productividad. Objetivo: Evaluar el efecto de la acidificación del agua de bebida sobre el rendimiento productivo, pH sanguíneo e intestinal, y morfología intestinal del pollo de engorde. Métodos: Se utilizaron 1.400 pollos de engorde de un día de edad para evaluar dos niveles de pH (4 y 6) en agua de bebida durante tres períodos (1-21, 1-28 y 1-42 días de edad). Los tratamientos consistieron en agua con una mezcla de ácido fórmico (31%), ácido propiónico (19%) y sus sales formiato de amonio (26%) y propionato de amonio (6%) en comparación con un grupo control (pH 8). Resultados: En comparación con el control, los grupos que recibieron agua a pH 6 (0,038 moles) continuamente durante 42 días tuvieron mejor (p≤0,01) rendimiento en términos de peso vivo (2,785 vs 2,691 kg) y conversión alimenticia (1,430 vs 1,463 kg/kg) así como un mayor número de vellosidades intestinales (59,0 vs 55,7). Adicionalmente, el pH sanguíneo e intestinal disminuyó vs el grupo control (7,75 vs 7,89; 6,32 vs 6,41, respectivamente). Conclusión: La mezcla de ácidos fórmico y propiónico y sus sales de amonio en el agua de bebida a pH 6 durante todo el ciclo productivo mejora los parámetros productivos en pollos de engorde, aumenta el número de vellosidades intestinales y reduce el pH de la sangre, duodeno e íleon.

Resumo Antecedentes: Recomendações para a aplicação de mistura de ácidos orgânicos e sais de amônio na água potável são necessárias para otimizar a produtividade em frangos de corte. Objetivo: Avaliar o efeito da acidificação da água de bebida no desempenho produtivo, pH sanguíneo e intestinal e morfologia intestinal. Métodos: 1.400 pintos de corte entre 1 e 42 dias de idade foram utilizados para avaliar dois níveis de pH (4 e 6) na água de beber entre três períodos (1-21, 1-28 e 1-42 dias de idade) de tratamentos em água com uma mistura de ácido fórmico 31%, ácido propiônico 19%, e seus sais formato de amônio 26% e propionato de amônio 6% em relação ao controle (pH 8). Resultados: Os grupos que receberam água continuamente pH 6 (0,038 mols), por 42 dias tiveram melhor desempenho em relação ao controle (p≤0,01) em termos de peso vivo (2,785 vs 2,691 kg) e conversão alimentar (1,430 vs 1,463 kg/kg), bem como aumento do número de vilosidades intestinais (59,0 vs 55,7), sangue e pH intestinal reduzidos vs controle (7,75 vs 7,89; 6,32 vs 6,41). Conclusão: A mistura dos ácidos fórmico e propiônico e seus sais de amônio na água de bebida em pH 6 durante o ciclo completo de produção melhorou os parâmetros de produção em frangos de 42 dias de idade e aumentou o número de vilosidades intestinais e uma redução no sangue, duodeno, e pH do íleo.

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Previous studies have shown that biofilm-forming bacteria are deficient in tricarboxylic acid (TCA) cycle metabolites, suggesting a relationship between these cellular processes. In this work, we compared the proteomes of planktonic vs biofilm cells from a clinical strain of Staphylococcus epidermidis using LC-MS/MS. A total of 168 proteins were identified from both growth conditions. The biofilm cells showed enrichment of proteins participating in glycolysis for the formation of pyruvate; however, the absence of TCA cycle proteins and the presence of lactate dehydrogenase, formate acetyltransferase, and acetoin reductase suggested that pyruvate was catabolized to their respective products: lactate, formate and acetoin. On the other hand, planktonic cells showed proteins participating in glycolysis and the TCA cycle, the pentose phosphate pathway, gluconeogenesis, ATP generation and the oxidative stress response. Functional networks with higher interconnection were predicted for planktonic proteins. We propose that in S. epidermidis, the relative absence of TCA cycle proteins is associated with the formation of biofilms and that lactate, formate and acetoin are the end products of partial glucose metabolism.

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BACKGROUND: L-tert-Leucine has been widely used in pharmaceutical, chemical, and other industries as a vital chiral intermediate. Compared with chemical methods, enzymatic methods to produce L-tert-leucine have unparalleled advantages. Previously, we found a novel leucine dehydrogenase from the halophilic thermophile Laceyella sacchari (LsLeuDH) that showed good thermostability and great potential for the synthesis of L-tertleucine in the preliminary study. Hence, we manage to use the LsLeuDH coupling with a formate dehydrogenase from Candida boidinii (CbFDH) in the biosynthesis of L-tert-leucine through reductive amination in the present study. RESULT: The double-plasmid recombinant strain exhibited higher conversion than the single-plasmid recombinant strain when resting cells cultivated in shake flask for 22 h were used. Under the optimized conditions, the double-plasmid recombinant E. coli BL21 (pETDute-FDH-LDH, pACYCDute-FDH) transformed 1 mol·L-1 trimethylpyruvate (TMP) completely into L-tert-leucine with greater than 99.9% ee within 8 h. CONCLUSIONS: The LsLeuDH showed great ability to biosynthesize L-tert-leucine. In addition, it provided a new option for the biosynthesis of L-tert-leucine.

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The rate constants and H/D kinetic isotope effect for hydrogen abstraction reactions involving isotopomers of methyl formate by methyl radical are computed employing methods of the variational transition state theory (VTST) with multidimensional tunneling corrections. The energy paths were built with a dual-level method using the moller plesset second-order perturbation theory (MP2) method as the low-level and complete basis set (CBS) extrapolation as the high-level energy method. Benchmark calculations with the CBSD-T approach give an enthalpy of reaction at 0 K for R1 (-4.5 kcal/mol) and R2 (-4.2 kcal/mol) which are in good agreement with the experiment, that is, -4.0 and - 4.8 kcal/mol. For the reactional paths involving the isotopomers CH3 + CH3 OCOH → CH4 + CH3 OCO and CH3 + CH3 OCOD → CH3 D + CH3 OCO, the value of kH /kD (T = 455 K) using the canonical VTST/small-curvature tunneling approximation method is 6.7 in close agreement with experimental value (6.2). © 2019 Wiley Periodicals, Inc.

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In this work, we present the development of a method for the determination of acetate and formate in vegetable oils by ion chromatography with conductometric detection following their extraction from samples using a diluted KOH solution. The extraction procedure was optimized using a multivariate approach. The application of a 24 full factorial design showed that the mass of sample, extraction time, and KOH concentration presented significant influence on the extraction of both acetate and formate, whereas the temperature presented little influence on the process. As a result, we set the extraction temperature at 22 °C and performed the multivariate optimization of the other variables using a Doehlert design. The optimum conditions were: 4.8 g of sample, 8 mmol L-1 KOH solution and 19 min extraction time. Six samples of vegetable oils (soybean, corn, canola, sunflower and olive) were analyzed and recovery tests provided recovery percentages in the range of 82-118%.

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Quantum tunneling paths are important in reactions when there is a significant component of hydrogenic motion along the potential energy surface. In this study, variational transition state with multidimensional tunneling corrections are employed in the calculations of the thermal rate constants for hydrogen abstraction from the cis-CH3 OCHO by O (3 P) giving CH3 OCO + OH (R1) and CH2 OCHO + OH (R2). The structures and electronic energies are computed with the M06-2X method. Benchmark calculations with the CBSD-T approach give an enthalpy of reaction at 0 K for R1 (-2.8 kcal/mol) and R2 (-2.5 kcal/mol) which are in good agreement with the experiment, i.e. -2.61 and -1.81 kcal/mol. At the low and intermediate values of temperatures, small- and large-curvature tunneling dominate the kinetics of R1, which is the dominant path over the range of temperature from 250 to 1200 K. This study shows the importance of multidimensional tunneling corrections for both R1 and R2, for which the total rate constant at 298 K calculated with the CVT/µOMT method is 8.2 × 10-15 cm3 molecule-1 s-1 which agrees well with experiment value of 9.3 × 10-15 cm3 molecule-1 s-1 (Mori, Bull. Inst. Chem. Res. 1981, 59, 116). © 2018 Wiley Periodicals, Inc.

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Enteric methane (CH4) emissions in ruminants have attracted considerable attention due to their impact on greenhouse gases and the contribution of agricultural practices to global warming. Over the last two decades, a number of approaches have been adopted to mitigate CH4 emissions. However, the mechanisms of methanogenesis have still not been fully defined. According to the genome sequences of M. ruminantium in the rumen and of M. AbM4 in the abomasum, the pathways of carbon dioxide (CO2) reduction and formate oxidation to CH4 have now been authenticated in ruminants. Furthermore, in the light of species or genera description of methanogens, the precursors of methanogenesis discovered in the rumen and research advances in related subjects, pathways of acetate dissimilation via Methanosarcina and Methanosaeta as well as metabolism of methanol to CH4 might be present in the rumen, although neither process has yet been experimentally demonstrated in the rumen. Herein the research advances in methanogenesic mechanisms including existing and potential mechanisms are reviewed in detail. In addition, further research efforts to understand the methanogenesis mechanism should focus on isolation and identification of more specific methanogens, and their genome sequences. Such increased knowledge will provide benefits in terms of improved dietary energy utilization and a reduced contribution of enteric CH4 emissions to total global greenhouse gas emissions from the ruminant production system.

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Enteric methane (CH4) emissions in ruminants have attracted considerable attention due to their impact on greenhouse gases and the contribution of agricultural practices to global warming. Over the last two decades, a number of approaches have been adopted to mitigate CH4 emissions. However, the mechanisms of methanogenesis have still not been fully defined. According to the genome sequences of M. ruminantium in the rumen and of M. AbM4 in the abomasum, the pathways of carbon dioxide (CO2) reduction and formate oxidation to CH4 have now been authenticated in ruminants. Furthermore, in the light of species or genera description of methanogens, the precursors of methanogenesis discovered in the rumen and research advances in related subjects, pathways of acetate dissimilation via Methanosarcina and Methanosaeta as well as metabolism of methanol to CH4 might be present in the rumen, although neither process has yet been experimentally demonstrated in the rumen. Herein the research advances in methanogenesic mechanisms including existing and potential mechanisms are reviewed in detail. In addition, further research efforts to understand the methanogenesis mechanism should focus on isolation and identification of more specific methanogens, and their genome sequences. Such increased knowledge will provide benefits in terms of improved dietary energy utilization and a reduced contribution of enteric CH4 emissions to total global greenhouse gas emissions from the ruminant production system.(AU)

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