Accumulation of ectoine in the halotolerant Brevibacterium sp. JCM 6894

Resting cells of Fusarium moniliforme strain MS31 produced (R)-1-phenylpropanol from propylbenzene. The components of the medium and the reaction conditions were adjusted to increase the specific activity of the hydroxylating enzyme involved. Glucose and sodium nitrate were selected as carbon and nitrogen sources, respectively. The substrate, propylbenzene, inhibited fungal growth and the activity of the enzyme. Acetoin added to the medium increased both growth and activity of the enzyme, and hydroxylation of propylbenzene increased by 1.4-fold. Maximum bioconversion of propylbenzene by resting cells of the fungus was at 25-30 degrees C and pH 7.0 with cells at concentration of 40 mg (dry) per milliliter of reaction mixture. Conversion was accelerated as soon as propylbenzene was added; slowing 2 h later. In the end, F. moniliforme strain MS31 produced (R)-1-phenylpropanol with an enantiomeric excess of 98% at the concentration of 16 mM (2.2 mg.ml(-1)).     

Effect of duration of osmotic downshock and coexisting glutamate on survival and uptake of ectoine in halotolerant Brevibacterium sp. JCM 6894

Halotolerant Brevibacterium sp. JCM 6894 that was subjected to an osmotic downshock (0.7 M NaCl to 0 M) was examined for its survival and uptake of ectoine in the presence of ectoine and/or carbon sources. In the presence of ectoine alone, the rates of ectoine uptake by the 1 h-downshocked cells were low and high in the absence and presence of 0.7 M NaCl, respectively, which were in parallel with the rates of cell growth. The presence of glutamate or amino acids together with ectoine exerted a stimulative effect on the survival of downshocked cells. The incubation time of the cells subjected to osmotic downshock strongly affected ectoine uptake as well as the cell growth of this strain, suggesting that the transporter of ectoine in the strain JCM 6894 was stimulated during the osmotic downshock for about 1 h. Different downshock strengths had marked effects on the rate of ectoine uptake when the downshocked cells were incubated in the presence of NaCl.     

Efficient utilization of ectoine by halophilic Brevibacterium species and Escherichia coli subjected to osmotic downshock

Halophilic and non-halophilic bacteria subjected to osmotic downshock, from 0.7 M NaCl to deionized water, were examined for their survival, with the uptake and utilization of the cyclic amino acid ectoine, one of the representative compatible solutes, being taken into account. The uptake of ectoine added externally and survival of the cells were monitored as a function of incubation time in the presence and absence of NaCl. The halophilic Brevibacterium sp. JCM 6894 and B. epidermidis JCM 2593 actively accumulated ectoine regardless of the presence of NaCl, which led to cell survival. Brevibacterium casei JCM 2594 belonging to the same Brevibacterium species, however, revealed Na+-dependence of its uptake activity of ectoine. Non-halophilic Escherichia coli K-12 did not accumulate ectoine, and thereby this strain failed to survive irrespective of whether NaCl was present. The physiological meanings of the downshock procedure are discussed in connection with the uptake and the subsequent utilization of ectoine.     

Supplementation effects of hydroxyectoine on proline uptake of downshocked Brevibacterium sp. JCM 6894

Downshock treatment of the halotolerant Brevibacterium sp. JCM 6894 was a prerequisite for proline uptake which is a function for cell survival. Hydroxyectoine served as an effective stimulator for the proline uptake and cell survival of the downshocked cells of this strain. Duration of osmotic downshock, downshock strength, and the kinds of osmolyte affected the efficient rate of growth (ERG) and the uptake of proline. A shorter duration of osmotic downshock, that is 相似文献   

利用胆固醇氧化酶转化胆固醇制备胆甾-4-烯-3-酮

用酶法催化氧化胆固醇制备胆甾-4-烯-3-酮相对于化学法合成具有反应简单、成本较低等优点.作者探讨了在正辛烷作为有机相的两相反应体系中,以胆固醇氧化酶催化氧化胆固醇制备胆甾-4-烯-3-酮的方法.在胆固醇质量浓度为40g/L,反应时间40min、反应温度40℃、磷酸缓冲液-正辛烷体积比32、通氧40L/h及搅拌转速300r/min下,胆固醇转化率达到92%,经薄板层析及紫外扫描,发现转化产物为单一的胆甾-4-烯-3-酮.     

胆固醇诱导甾短杆菌发酵产胆固醇氧化酶能力的研究

利用胆固醇诱导甾短杆菌发酵来提高胆固醇氧化酶产量;通过对单因素的研究,选取影响比较显著的3个因素:胆固醇质量浓度、吐温-80添加量、超声波功率,并利用Box-Behnken试验设计和响应曲面分析法进一步研究得到结果:甾短杆菌产酶的最佳条件是当超声时间为20min时,胆固醇质量浓度为3.30g/L、吐温-80添加量为3.72mL/L、超声波功率为80W,在此条件下测得的胆固醇氧化酶产量为731.967U/L。比未使用胆固醇诱导产酶时,酶产量提高了1.17倍。     

短杆菌属产胆固醇氧化酶的发酵条件优化

短杆菌属(Brevibacterium sp.)是胆固醇氧化酶高产菌,对其进行底物诱导及发酵条件的优化,其最适培养基为蔗糖0.3%,酵母膏0.2%,蛋白胨0.3%,牛肉膏0.3%,K2HPO4 0.1%,MgSO4 0.05%,pH6.8。最适培养条件为接种量5%,24℃培养20h,通气量为50mL培养基/250mL三角瓶,200r/min。结果表明,胆固醇氧化酶的酶活力可达到2439U/L,比未优化前195U/L提高了12倍。在pH6.5和温度54℃条件下测得酶米氏常数Km值为7.1×10-5 mol/L。     

胆固醇氧化酶高产菌株的复合诱变选育

为进一步提高产酶水平,本实验采用超声波联合亚硝基胍的复合诱变方法处理胆固醇氧化酶产生菌(甾短杆菌),通过1mg/mL亚硝基胍和超声(200W,50kHz,35min)同时处理细胞悬液,获得一株红色突变株,其产酶活力从0.5U/mL提高到1.21U/mL,酶活提高了140%。证明该联合诱变手段对甾短杆菌产胆固醇氧化酶具有良好的诱变效果。     

Bioconversion of yolk cholesterol by extracellular cholesterol oxidase from Brevibacterium sp.

An efficient process for reducing yolk cholesterol by enzymatic treatment was developed in this paper. Extracellular cholesterol oxidase (COD) from a mutant Brevibacterium sp. ODG-007, showed a strong capacity in bioconversion of yolk cholesterol to cholest-4-en-3-one, especially supplemented with NaCl and lipase C, as a yolk granule solubilizer. The bioconversion process was investigated first, to obtain basic information of the process and was further optimized by analysis of parameters, including COD concentration, dilution ratio and incubation time on the cholesterol conversion, employing Response Surface Methodology (RSM) and Central Composite Design (CCD). Under the optimum operational conditions: COD concentration of 5.39 U/g yolk powder, water: solid ratio of 3.54 and incubation time of 13.75 h, up to 85.6% yolk cholesterol was reduced, and the remaining cholestenone, an effective anti obesity medicine in the product, may raise its commercial value.     

Production and characterization of ectoine by Marinococcus sp. ECT1 isolated from a high-salinity environment

A halophilic bacterium isolated from a salt environment in southern Taiwan was identified as a Marinococcus sp. ECT1. This bacterium could synthesize and accumulate intracellular ectoine as a compatible solute capable of resisting osmotic stress in a hyper-osmotic environment. This study also developed a semi-synthesized medium (YAMS medium), capable of facilitating the growth of this Marinococcus sp. ECT1 with 600 mg/L crude ectoine production. Moreover, Marinococcus sp. ECT1 was grown on YAMS medium containing different initial yeast extract concentrations (C(YE)) (0 to 60 g/L) to demonstrate how C(YE) affects crude ectoine production. While the maximum cell concentration was increased by 23-fold when the C(YE) was 40 g/L, the maximum crude ectoine production reached 2.5 g/L when C(YE) was 40 g/L. In addition to demonstrating the success of the fermentation strategy of ectoine in increasing the production and production yield, experimental results further demonstrated that the fermentation medium of ectoine is highly promising for commercialization. Furthermore, the molecular weight and chemical structure of ectoine were identified and characterized by FAB-MS and (1)H-NMR.     

Brevibacterium sp.DGCDC-82发酵罐中生产胆固醇氧化酶

用Brevibacterium sp.DGCDC-82在7L发酵罐中分批培养.分别对添加剂吐温-80、培养温度、培养基的pH、通风量和搅拌速度在胆固醇氧化酶的生产中的影响进行了研究.结果显示以上条件均对产酶有影响.在不同的发酵阶段改变发酵操作条件,发酵20 h最高酶活可达1203U/L,生产强度可达60 U/(L·h).既有效地提高了胆固醇氧化酶的产量,又防止了发酵过程中的泡沫外溢.     

A cytoplasmic xylanase (XynX) of Aeromonas caviae ME-1 is released from the cytoplasm to the periplasm by osmotic downshock

Aeromonas caviae ME-1 is a multiple xylanase-producing gram-negative bacterium which was isolated from the gut contents of a wild silkworm, Samia cynthia pryeri. One of the xylanases produced by A. caviae ME-1, XynX (38 kDa, family 10 xylanase), hydrolyzes xylan to xylobiose and xylotetraose as final degradation products. Generally, xylanases are extracellular or cell surface enzymes. However, XynX is not exported to the extracellular fluid by A. caviae ME-1 and an Escherichia coli transformant harboring the xynX gene. In this study, we investigated the intracellular localization of XynX in A. caviae ME-1 and an E. coli transformant. XynX was found in the cytoplasm when the cells were grown under normal culture conditions. However, XynX was released from the cytoplasm to the periplasm during osmotic downshock. This release of XynX in the E. coli transformant was blocked in the presence of gadolinium chloride, which has been reported to be an inhibitor of bacterial mechanosensitive channels.     

胆固醇氧化酶的发酵条件及酶学性质研究

Brevibacterium sp．可以发酵生产胆固醇氧化酶,实验中对该菌种进行了底物诱导及发酵条件的优化, 确定其最适培养基为(%)：蔗糖0．3,酵母膏0．2,蛋白胨0．3,牛内膏0．3,K_2PO_4 0．1,MgSO_4 0．05,pH6．8。最适培养条件为：接种量5%,24℃培养20h,通气量为50mL 培养基/250mL 三角瓶,200r/min。在最适培养基及最适条件下,胆固醇氧化酶的酶活力可达到24．01U/mg,比未优化前1．71U/mg 提高了14倍。该酶具有较强的酸碱稳定性和热稳定性,最适 pH 为6．5,最适温度为54℃。在最适 pH 和温度条件下测得该酶 km 值为7．1 ×10~(-5)mol/L。     

响应面分析应用于短杆菌产酶工艺的优化

本文研究了用响应面分析法(RSM)优化短杆菌产胆固醇氧化酶的工艺，发现胆固醇添加量及超声处理时间是影响短杆菌产酶最重要的因素。在模拟优化的条件下：胆固醇为4．076g／L，吐温-80为0．2932％(v／v)，照射时间为22．361min，COD最大产量1．483U／mL。     

Humectant permeability influences growth and compatible solute uptake by Staphylococcus aureus subjected to osmotic stress

The effects of different humectants (sodium chloride, sucrose, and glycerol) on the growth of and compatible solute (glycine betaine, proline, and carnitine) uptake by the osmotolerant foodborne pathogen Staphylococcus aureus were investigated. While growth in the presence of the impermeant humectants sodium chloride and sucrose induced the accumulation of proline and glycine betaine by cells, growth in the presence of the permeant humectant glycerol did not. When compatible solutes were omitted from low-water-activity media, growth was very poor in the presence of impermeant humectants. In contrast, the addition of compatible solutes had essentially no effect on growth when cells were grown in low-water-activity media containing glycerol as the humectant. Carnitine was found to accumulate to high intracellular levels in osmotically stressed cells when proline and glycine betaine were absent, making it a potentially important compatible solute for this organism.     

Drying of plums (Prunus sp,c.v Gulfblaze) treated with KCl in the field and subjected to pulsed vacuum osmotic dehydration

The pulsed vacuum osmotic dehydration (PVOD) promotes more homogeneous concentration profiles in the product and quality improvement of several fruits. The objective of this work was to study the drying of plums submitted to treatments of plants manure with KCl and PVOD (5” c.a., 10 min). Experimental planning was done with the following independent variables: doses of KCl (400, 700 and 1000 g/plant), concentration of sucrose solution (40; 50 and 60 ºBrix) and drying temperature (50, 60 and 70C). The tested variables were: color, shrinkage, visual quality and rehydration. Temperature leads to a skin browning at fruit pulps and lower visual quality. The treatment with KCl leads to final products with lower moisture content. The higher the values of all the independent variables, the lower the shrinkage and the rehydration capacity. Plums submitted to convective drying with previous PVOD promote a new product with good visual quality and satisfactory shrinkage.     

Antioxidant and antimicrobial properties of organic fruits subjected to PEF-assisted osmotic dehydration

The effect of PEF pre-treatment prior to osmotic dehydration on mass transfer parameters, colour, antioxidant and antimicrobial properties in organic strawberries and kiwifruits was evaluated. An increase of water loss in both fruits upon the application of combined processes was noticed (up to 21.6%), while a decrease of solid gain was observed only in kiwifruit samples dehydrated in sucrose (about 45%). In general, the combined treatments were beneficial for colour maintenance in both fruit tissues. The antioxidant capacity (DPPH) and activity (ORAC) increased after PEF treatment, however, all the combined treatments reduced significantly these values (of about 20 and 28% for strawberry and of about 56 and 35% for kiwifruit, respectively for DPPH and ORAC methods). In general, PEF treatment alone was also effective with regard to an increase in the antimicrobial activity of the samples against the tested microorganisms (B. subtilis, E.coli, S. cerevisiae).Industrial relevancePEF pre-treatment coupled with osmotic dehydration could be applied at industrial level to obtain semi-dried fruit products. Moreover, both processes could be used as pre-treatments for drying process, in order to develop healthy and microbiologically stable fruit snacks. In fact, in the present work we observed that PEF pre-treatment alone promoted higher antioxidant and antimicrobial activity. The combined process decreased both parameters, suggesting that an accurate study is necessary to evaluate the benefits of these processes in terms of bioactive compounds retention and time and energy consumption in further drying process. The results of the present study could be used as a starting point for the industries to design novel products with intermediate moisture content intended for further processing.     

从乳化体系中分离纯化短杆菌产胆固醇氧化酶

添加剂W对酶的分离纯化造成很大困难,用异丙醇沉淀发酵液的同时加入(NH4)2SO4能够有效地破除乳化体系,去除添加剂W,酶收率达到90%.在pH值为8.0的条件下用SepharoseDEAEFastFlow离子交换透析酶液,比酶活从3.21U/mg提高到29.21U/mg,酶收率达70.1%.     

Enhanced glutamic acid production of Brevibacterium sp. with temperature shift-up cultivation

For cells of Brevibacterium sp. under conditions of biotin limitation, the efflux of metabolites through the cell membrane was affected by temperature. After the temperature shift-up from 30 degrees C to 38 degrees C, both the specific production rate of glutamic acid and the excretion of intracellular materials, such as glucose-6-phosphate and nucleotides, were increased simultaneously. For the production of glutamic acid, not only the yield but also the specific production rate was increased by the temperature shift-up.     

Physiology of pre-cut mango. I. ACC and ACC oxidase activity of slices subjected to osmotic dehydration

Physiologically mature mangoes were ripened for 6 days at 24°C and 98% relative humidity. Slices from these fruits were osmotically dehydrated by immersion in sucrose 65°Brix at 30°C and 211 mbar vacuum during 30 min. Slices not subjected to osmotic dehydration (NOD) and slices with osmotic dehydration (OD) were stored at 24, 13 or 5°C. The respiration rate of both slice types was affected by the storage temperature. 1-Aminocyclopropane-1-carboxylic acid (ACC) synthesis indicated activity of ACC synthase in both slices as well as in the whole fruit. ACC oxidase activity was greater in OD slices as compared to NOD and that was associated to better membrane stability. OD favored compaction of external layer in slices. No ethylene was detected in slices; however, the tissues did not lose their ability to synthesize ethylene. Results suggest that OD under vacuum may be beneficial as a pre-treatment of mango slices for longer shelf life under refrigeration.