Enhanced production of lactic acid through the use of a novel aqueous two-phase system as an extractive fermentation system

 In order to enhance the productivity of lactic acid and reduce the end-product inhibition of fermentation, the partitioning and growth of four different strains of lactic acid bacteria in three different aqueous two-phase systems were studied. Polyethyleneglycol/ dextran, polyethyleneglycol/hydroxypropyl starch polymer (HPS), and a random copolymer of ethylene oxide and propylene oxide (EO-PO)/HPS were used as polymer systems. One strain each of Lactococcus lactis subsp. lactis and of Lactobacillus delbrueckii subsp. delbrueckii partitioned completely to the interface and bottom phase in two-phase systems with low polymer concentrations of EO-PO/HPS100 and EO-PO/ HPS200. The growth and production of lactic acid by two of three L. lactis strains in a two-phase system with 5.5% (w/w) EO-PO and 12.0% (w/w) HPS100 were reduced by less than 10% compared with a reference fermentation in a normal growth medium. The viability of L. lactis subsp. lactis ATCC 19435 was maintained for at least 50 h and with four top-phase replacements during extractive fermentation in the EO-PO/HPS100 system. Moreover, when cell density reached the stationary phase in the first extractive fermentation, the lactate production in this aqueous two-phase system was maintained. Received: 2 October 1995/Received revision: 16 January 1996/Accepted: 22 January 1996     

Glucose metabolism by brown trout peripheral blood lymphocytes

Glucose metabolism in peripheral blood lymphocytes from the brown trout Salmo trutta has been studied. Glucose is taken up by means of a sodium-independent saturable process (K _m=10.8 mmol·l^-1), as well as by simple diffusion. Once within the cell, most of glucose is directed to lactate production through either the Embden-Meyerhof pathway or the hexose-monophosphate shunt. Rates of lactate formation are higher than rates of CO₂ formation. Glutamine does not exert an effect on either glucose uptake or glucose metabolism. The present study provides information regarding the nature of energy sources for different cell types in salmonids.Abbreviations 3-OMG 3-O-methyl glucose - EM Embden-Meyerhoff pathway - G6D glucose-6-phosphate dehydrogenase - HK hexokinase - HMS hexose monophosphate shunt - ICDH isocitrate dehydrogenase - K _m apparent Michaelis constant - LDH lactate dehydrogenase - MCB modified Cortland buffer - PBL peripheral blood lymphocytes - PFK fructose-6-phosphate kinase - PK pyruvate kinase - RBC red blood cells - V _max maximal rate of uptake     

Low genetic diversity and population connectivity fuel vulnerability to climate change for the Tertiary relict pine Pinus bungeana

Endemic species are important components of regional biodiversity and hold the key to understanding local adaptation and evolutionary processes that shape species distributions. This study investigated the biogeographic history of a relict conifer Pinus bungeana Zucc. ex Endl. confined to central China. We examined genetic diversity in P. bungeana using genotyping-by-sequencing and chloroplast and mitochondrial DNA markers. We performed spatial and temporal inference of recent genetic and demographic changes, and dissected the impacts of geography and environmental gradients on population differentiation. We then projected P. bungeana's risk of decline under future climates. We found extremely low nucleotide diversity (average π 0.0014), and strong population structure (global F_ST 0.234) even at regional scales, reflecting long-term isolation in small populations. The species experienced severe bottlenecks in the early Pliocene and continued to decline in the Pleistocene in the western distribution, whereas the east expanded recently. Local adaptation played a small (8%) but significant role in population diversity. Low genetic diversity in fragmented populations makes the species highly vulnerable to climate change, particularly in marginal and relict populations. We suggest that conservation efforts should focus on enhancing gene pool and population growth through assisted migration within each genetic cluster to reduce the risk of further genetic drift and extinction.     

Systematics of Mukdenia and Oresitrophe (Saxifragaceae): Insights from genome skimming data

Oresitrophe and Mukdenia (Saxifragaceae) are epilithic sister genera used in traditional Chinese medicine. The taxonomy of Mukdenia, especially of M. acanthifolia, has been controversial. To address this, we produced plastid and mitochondrial data using genome skimming for Mukdenia acanthifolia and Mukdenia rossii, including three individuals of each species. We assembled complete plastomes, mitochondrial CDS and nuclear ribosomal ETS/ITS sequences using these data. Comparative analysis shows that the plastomes of Mukdenia and Oresitrophe are relatively conservative in terms of genome size, structure, gene content, RNA editing sites and codon usage. Five plastid regions that represent hotspots of change (trnH-psbA, psbC-trnS, trnM-atpE, petA-psbJ and ccsA-ndhD) are identified within Mukdenia, and six regions (trnH-psbA, petN-psbM, trnM-atpE, rps16-trnQ, ycf1 and ndhF) contain a higher number of species-specific parsimony-informative sites that may serve as potential DNA barcodes for species identification. To infer phylogenetic relationships between Mukdenia and Oresitrophe, we combined our data with published data based on three different datasets. The monophyly of each species (Oresitrophe rupifraga, M. acanthifolia and M. rossii) and the inferred topology ((M. rossii, M. acanthifolia), O. rupifraga) are well supported in trees reconstructed using the complete plastome sequences, but M. acanthifolia and M. rossii did not form a separate clade in the trees based on ETS + ITS data, while the mitochondrial CDS trees are not well-resolved. We found low recovery of genes in the Angiosperms353 target enrichment panel from our unenriched genome skimming data. Hybridization or incomplete lineage sorting may be the cause of discordance between trees reconstructed from organellar and nuclear data. Considering its morphological distinctiveness and our molecular phylogenetic results, we strongly recommend that M. acanthifolia be treated as a distinct species.     

First chemical synthesis of a scorpion alpha-toxin affecting sodium channels: the Aah I toxin of Androctonus australis hector.

Aah I is a 63-residue alpha-toxin isolated from the venom of the Buthidae scorpion Androctonus australis hector, which is considered to be the most dangerous species. We report here the first chemical synthesis of Aah I by the solid-phase method, using a Fmoc strategy. The synthetic toxin I (sAah I) was renatured in DMSO-Tris buffer, purified and subjected to thorough analysis and comparison with the natural toxin. The sAah I showed physico-chemical (CD spectrum, molecular mass, HPLC elution), biochemical (amino-acid composition, sequence), immunochemical and pharmacological properties similar to those of the natural toxin. The synthetic toxin was recognized by a conformation-dependent monoclonal anti-Aah I antibody, with an IC50 value close to that for the natural toxin. Following intracerebroventricular injection, the synthetic and the natural toxins were similarly lethal to mice. In voltage-clamp experiments, Na(v) 1.2 sodium channel inactivation was inhibited by the application of sAah I or of the natural toxin in a similar way. This work describes a simple protocol for the chemical synthesis of a scorpion alpha-toxin, making it possible to produce structural analogues in time.     

ZAKβ antagonizes and ameliorates the cardiac hypertrophic and apoptotic effects induced by ZAKα

ZAK (sterile alpha motif and leucine zipper containing kinase AZK), a serine/threonine kinase with multiple biochemical functions, has been associated with various cell processes, including cell proliferation, cell differentiation, and cardiac hypertrophy. In our previous reports, we found that the activation of ZAKα signaling was critical for cardiac hypertrophy. In this study, we show that the expression of ZAKα activated apoptosis through both a FAS‐dependent pathway and a mitochondria‐dependent pathway by subsequently inducing caspase‐3. ZAKβ, an isoform of ZAKα, is dramatically expressed during cardiac hypertrophy and apoptosis. The interaction between ZAKα and ZAKβ was demonstrated here using immunoprecipitation. The results show that ZAKβ has the ability to diminish the expression level of ZAKα. These findings reveal an inherent regulatory role of ZAKβ to antagonize ZAKα and to subsequently downregulate the cardiac hypertrophy and apoptosis induced by ZAKα.