Preparation of L (+) beta-hydroxyisobutyric acid by bacterial oxidation of isobutyric acid

A process for the bacterial oxidation of isobutyric acid to L(+) β-hydroxyisobutyric acid has been developed. The strain of Pseudomonas putida (ATCC 21244) used in this fermentation was isolated from local soil. The process was carried out in a 15-liter fermentor over a period of 70 hr and produced L(+) β-hydroxyisobutyric acid in conversions as high as 48%. Hydroxylation of the methyl group of isobutyric acid has special interest because it is difficult to perform chemically. The useful chemical syntheses of β-hydroxyisobutyric acid available at present do not start with isobutyric acid and are not stereospecific.     

不同的中和剂对L(+)-乳酸发酵的影响

分别利用CaCO3、6 mol/L氨水和6 mol/L NaOH溶液调控乳酸发酵过程的pH,得到的乳酸浓度为169.1g/L、187.9g/L和170.1g/L(以发酵液的初始体积计算),分别是无pH调控发酵过程的4.9倍、5.4倍和4.9倍;得到的OD620分别为19.3、21.6和16.4,分别是无pH调控(OD620为8.5)的2.3倍、2.5倍和1.9倍.相对于氨水和NaOH来说,CaCO3粉末是一种缓慢型的酸中和剂,pH调节能力有限,只能将pH维持在4.9～5.2.但CaCO3可以将乳酸以生成乳酸钙的形式沉淀下来,给下游乳酸的分离提取带来一定的方便.因此对于传统的分批式发酵,CaCO3仍不失为一种较好的选择.氨水和NaOH溶液都可以很好地将发酵液的pH调控在6.0,其中氨水是一种最理想的酸中和剂,既有利于乳酸的生物合成又能促进乳酸菌的生长.     

Leucosporidium fellii sp. nov., a basidiomycetous yeast that degrades L(+)-tartaric acid

A new species of basidiomycetous yeast Leucosporidium fellii was isolated from soil in Portugal on a selective L(+)-tartaric acid medium. This yeast is self-sporulating but forms dikaryotic hyphae with clamp connections and is presumably homothallic. It differs from the type strain of Leucosporidium scottii in its life cycle, assimilation pattern and guanine-cytosine content and from the other described Leucosporidium species by additional characteristics.     

Occurrence of (+)-7-iso-jasmonic acid inVicia faba L. and its biological activity

The plant growth regulator (–)-jasmonic acid (JA) and its stereoisomer (+)-7-iso-jasmonic acid (7-iso-JA) have been isolated from young fruits ofVicia faba L. and identified by TLC, GC, GC-MS, and chemical transformation. Different isolation procedures gave different ratios of JA/7-iso-JA because of partial isomerization of (+)-7-iso-JA to (–)-JA. Optimal conditions, excluding artificial isomerization, were checked by the addition of [U-¹⁴C]-7-iso-JA. The naturally occurring isomer ratio was determined to be 65% (–)-JA: 35% (+)-7-iso-JA in immature broad bean fruits. The biological activities of both isomers of JA have been studied using several bioassays. Growth of wheat and GA₃-stimulated dwarf rice seedlings is inhibited more effectively by (+)-7-iso-JA than by (–)-JA. In growing seedlings of barley and oat, both isomers caused a senescence-like bleaching effect characterized by chlorophyll and carotenoid decrease. The free acids are more active than their methyl esters in intact barley plants in contrast to results obtained in leaf segment tests. Highest activity was obtained with (+)-7-iso-JA.     

Direct fermentation of corn to L(+)-lactic acid byRhizopus oryzae

Summary Rhizopus oryzae NRRL 395 was found capable of fermenting ground corn directly to L(+)-lactic acid in the presence of calcium carbonate. The average yield of L(+)-lactic acid was more than 44% on the basis of the amount of total carbohydrate as glucose consumed.     

Optimization of L(+)-lactic acid production employing statistical experimental design

Summary An orthogonal 2³-factorial experimental design was used to optimize L(+)-lactic acid production byLactobacillus casei. With a 22 % (v/v) inoculum the optimum concentration of yeast extract for maximum lactic acid concentration and yield was about 2 % (w/v) and that of the initial glucose 9 to 11 %.     

Modeling of continuous L(+)-lactic acid production with immobilized R. oryzae in an airlift bioreactor

Continuous L(+)-lactic acid production was carried out in an airlift bioreactor with immobilized R. oryzae in polyurethane foam cubes. In a pseudo-steady state, the productivity of lactic acid increased with increasing dilution rate or feeding glucose concentration. A double-layer reaction-diffusion model for the pseudo-steady state process was developed to describe the bioreaction system. Using independently determined model parameters, the model prediction agreed well with the experimental results. Therefore, the model can be employed to understand the fermentation behavior, and for the process design and optimization.     

Formation of aminium lactates in lactic acid fermentation preparation and characterization of 1,4-piperazinium-(L,L)-dilactate obtained from L(+)-lactic acid (part I)

The potential for the production of 1,4-piperazinium-(L, L)-dilactate from L(+)-lactic acid preparations obtained by fermentation was studied. Piperazinium dilactate was found to be a very suitable source material for poly(lactic acid) production. In a novel polymerization process, the intermediate dilactide was directly formed in the salt melt at a moderate temperature. High-performance cultivation of Lactobacillus paracasei on a glucose-MRS medium was carried out using high-viability inocula. After the cell mass had been removed from the fermentation broth by centrifugation and/or ultrafiltration, the lactic acid solution was concentrated to 45% [w/w] by a two-stage electrodialysis process. Two methods of preparing 1,4-piperazinium dilactate were developed: the first from the medium-concentrated lactic acid (45%) and the second from a highly-concentrated lactic acid (85%) obtained by evaporation from the first one. Because there were no physical data on 1,4-piperazinium-(L, L)-dilactate in specialized literature, the pure product was characterized according to its solubility characteristics, melting point and spectroscopic analysis.     

根瘤菌BK-20固定化细胞生产L(+)-酒石酸

顺式环氧琥珀酸水解酶(CESH)是根瘤菌BK-20生产L(+)-酒石酸的关键酶。为提高其生产效率和生产稳定性,首先优化根瘤菌BK-20的产酶条件,然后利用固定化细胞连续生产L(+)-酒石酸。结果显示,优化后游离细胞酶活达(3 498.0±142.6)U/g,较优化前提高643%。固定化细胞酶活达(2 817.2±226.7)U/g,其最适包埋剂、菌体浓度和凝胶浓度分别为海藻酸钠,10%(W/V)和1.5%(W/V)。固定化细胞连续反应10批后,其形状和酶活均无明显改变,单批次转化率达98%以上,具有良好的生产稳定性。     

L(+)-Lactic acid from sweet sorghum by submerged and solid-state fermentations

Sweet sorghum was used as the raw material for the lactate production by a strain of Lactobacillus paracasei. The submerged conversion of sugar juice obtained from sweet sorghum by extraction could be accomplished with the same efficiency as observed in a control experiment with MRS-glucose medium (final lactate concentration of 88–106 g/l, lactate yield of 91–95%, duration of the fermentation of 24–32 h). Finely ground stalks of sorghum served as the substrate in the solid-state fermentation. The lactate accumulation in the solid medium and the lactate yield were optimized up to values comparable with the results from the submerged fermentation (final lactate concentration of 90 g/kg, lactate yield of 91–95%). However, the duration of the fermentation amounted to 120–200 h in the solid-state process. The data from a series of experiments performed at variable values of temperatures between 30°C and 36°C and initial sugar concentrations between 60 g/kg and 115 g/kg, and degrees of moisture between 78% and 82% was the basis of a polynomial multidimensional regression. As a result, simple three-dimensional model functions were obtained for the maximum productivity of lactate formation, the lactate yield and the time required for a 90% conversion.     

Production of L(+)-lactic acid with Rhizopus oryzae immobilized in polyurethane foam cubes

Summary Polyurethane foam cubes were employed as carriers to immobilize Rhizopus oryzae for L(+)-lactic acid production. The immobilizing capacity reached 450 g-fresh cell/l-cube. The production rate of L(+)-lactic acid could be threefold increased by using the immobilized R. oryzae. The immobilized cells could be steadily used in repetitive fermentations for more than 10 batches.