5-氨基乙酰丙酸脱水酶缺失对大肠杆菌生长的影响

5-氨基乙酰丙酸(ALA)脱水酶直接关系到ALA的积累,研究该酶突变对细胞的影响对生物法生产ALA具有重要意义,然而目前这方面认识比较混乱.本研究通过无痕敲除Ecoli MG1655菌株的ALA脱水酶的结构基因hemB,发现ALA脱水酶酶活大幅降低,且突变株生长受到极大的影响,但是仍然有10%的残余酶活支持细胞微弱且不...     

Effects of medium composition on production of 5-aminolevulinic acid by recombinant Escherichia coli

The recombinant Escherichia coli BL21(DE3) harboring hemA from Agrobacterium radiobacter, which was engineered in our previous work, was used for the extracellular production of 5-aminolevulinic acid (ALA). The effects of various physiological factors, such as the concentrations of precursors (glycine, succinic acid and glucose) and the inhibitor 5-aminolevulinate dehydratase (levulinic acid), on the ALA accumulation in the fermentation broth were investigated in both shake flasks and a jar fermentor. Among these precursors, glycine exhibited the strongest ability to inhibit cell growth, while glucose mainly inhibited ALA formation. The optimum initial concentrations of glycine, succinic acid and glucose were found to be 2.0, 10.0 and 2.0 g/l, respectively. Levulinic acid (LA; 30 mM) was fed to the fermentation broth at the end of the exponential cell growth phase (about 8 h), and the intracellular activity of ALA dehydratase was efficaciously suppressed. Repeating the optimum composition of the medium in a stirred tank fermenter resulted in 1.49 g/l ALA. Furthermore, the fed batch of the precursors and inhibitor further increased ALA production up to 3.01 g/l.     

花椒籽油α-亚麻酸提取技术的研究进展

α-亚麻酸（ALA）是n-3多不饱和脂肪酸中唯一的必需脂肪酸,具有益智、保护视力、降低胆固醇与血脂、预防心脑血管疾病、增强免疫力、抗炎、抑制癌症的发生及转移、抗氧化、延缓衰老及减肥等生理功能,在医药、保健品、食品等领域有着广阔应用前景。本文综述了目前花椒籽油α-亚麻酸提取技术的最新研究进展,总结了这些方法的原理、优点及研究现状,并在此基础上对其提取技术的前景进行了展望,以期为将来更加深入地研究和开发花椒籽提供一定的理论基础。      

Stability of α-Linolenic Acid and Secoisolariciresinol Diglucoside in Flaxseed-Fortified Macaroni

Research was conducted to determine the stability of secoisolariciresinol diglucoside (SDG) and α‐linolenic acid (ALA) in flaxseed‐fortified macaroni. Macaroni was fortified with whole ground flaxseed (GWF) at levels of 10% to 20% and then dried under low temperature (LT, 40°C), high temperature (HT, 70°C), or ultrahigh temperature (UHT, 90°C). Macaroni was also fortified with 15% ground hull (GHF) or steam‐treated whole ground flaxseed (GSWF) and dried under UHT. The dried macaroni was stored for 32 wk under ambient conditions. Approximately 80% to 95% of the SDG was recovered, indicating that SDG was stable during the 32‐wk storage period. Total lipid and ALA levels in all flaxseed macaroni treatments remained unchanged throughout the 32‐wk storage. This observation was consistent across the drying conditions and flaxseed addition levels. Conjugated diene (CD) values indicated that macaroni fortified with GWF did not oxidize significantly during the 32‐wk storage for the macaroni dried under HT or UHT. However, a significant increase (P <0.05) in CD values for macaroni containing 10% and 20% flaxseed and dried using LT was observed at the 32‐wk storage period. Headspace volatile concentrations did increase over the storage period for macaroni containing GWF, but the increase was not significant. Significant increases (P < 0.05) in oxidation were found by 24 wk in GHF‐ and GSWF‐fortified macaroni. GWF macaroni dried at UHT, HT, or LT could be used as a way to improve our dietary consumption of ALA and SDG. However, use of steam as a method to inactivate unwanted enzyme activity is not recommended.     

5-氨基乙酰丙酸对苹果幼果多酚含量、苯丙氨酸解氨酶活性及其基因表达的影响

探究5-氨基乙酰丙酸（aminolevulinic acid,ALA）处理对苹果幼果酚类物质、苯丙氨酸解氨酶（phenylalanin ammonia-lyase,PAL）活性及其基因表达量的影响。在苹果疏果期前,利用不同质量浓度ALA处理苹果幼果,采用紫外分光光度法测定ALA处理后12 d内苹果多酚和PAL活性,利用荧光定量法测定苹果幼果PAL基因表达量。结果表明：ALA处理质量浓度在300 mg/L以内,随着质量浓度提高,苹果多酚含量、PAL酶活性及其基因表达量均升高,到400 mg/L时各项指标均表现出下降趋势;相同质量浓度ALA处理苹果幼果后,幼果的上述3 项指标均随时间延长而明显提高,在第9天时达到最高值,12 d后开始下降。为提高苹果疏果多酚含量,实现疏果的最大利用率,生产中需要选择适宜的ALA处理浓度和时间采集幼果。     

不同类型n-3多不饱和脂肪酸对心血管疾病的防治作用及其机制研究进展

3种主要的食源性n-3多不饱和脂肪酸包括α-亚麻酸(ALA)、二十碳五烯酸(EPA)和二十二碳六烯酸(DHA)。综述了ALA、EPA和DHA降低甘油三酸酯水平和血小板凝集,改善炎症和氧化应激指标以及改善血管和心脏血液动力学的功能,从而对动脉粥样硬化等心血管疾病起到防治作用。此外,总结了联合使用ALA、EPA和DHA防治心血管疾病的作用,并进行了展望。     

Lower pregnancy losses in lactating dairy cows fed a diet enriched in alpha-linolenic acid

The objectives were to determine if a diet enriched in α-linolenic acid (ALA) would influence ovarian function, early embryo survival, conception rates, and pregnancy losses in lactating dairy cows. Beginning 28 d before breeding, Holstein cows (55 ± 22 d postpartum; mean ± SD) were assigned to diets supplemented with either rolled flaxseed (FLAX; 56.7% ALA, n = 62) or rolled sunflower seed (SUNF; 0.1% ALA, n = 59) to provide approximately 750 g of oil/d. Diets continued for 32 d after timed artificial insemination (TAI, d 0) following a Presynch/Ovsynch protocol. Barley silage- and barley grain-based TMR were formulated to meet or exceed National Research Council requirements. Metabolizable protein and net energy for lactation concentrations were similar in the 2 diets. Based upon a mean dry matter intake of 22 kg/d, cows fed FLAX or SUNF consumed > 410 g or < 1 g of ALA, respectively. Pregnancy was confirmed by ultrasound 32 d after TAI. Nonpregnant cows were placed on a second Ovsynch regimen and reinseminated 42 d after first TAI, and received oilseeds for 32 d after second TAI. Relative to prediet levels, FLAX increased the ALA content of milk by 187%. Ovarian ultrasonography was performed in 8 cows per diet; the mean diameter of ovulatory follicles was larger in cows fed FLAX compared with SUNF (16.9 ± 0.9 vs. 14.1 ± 0.9 mm), but follicle number, corpus luteum size, and plasma progesterone concentrations remained unaffected. Presumptive conception (progesterone < 1 ng/mL on d 0 and > 1 ng/mL on d 21) rates to first TAI were greater in FLAX than in SUNF (72.6 vs. 47.5%). Pregnancy losses were lower in cows fed FLAX (9.8%) compared with those fed SUNF (27.3%). Including flaxseed in the ration of dairy cows increased the size of the ovulatory follicle and reduced pregnancy losses.     

Production of biomass and extracellular 5-aminolevulinic acid by Rhodopseudomonas palustris KG31 under light and dark conditions using volatile fatty acid

Kinetic parameters for growth and extracellular 5-aminolevulinic acid (ALA) production of Rhodopseudomonas palustris KG31 under light and dark conditions in a medium containing volatile fatty acids (VFA) as the carbon sources were estimated using a Gompertz model. The lag phase for growth and the maximum specific growth rate under microaerobic-light cultivations were 7.29-12.49 h and 0.038-0.094 h(-1), respectively, whereas under aerobic-dark cultivations, they were 2.03-14.25 h and 0.016-0.022 h(-1), respectively. The lag phase for extracellular ALA production and the maximum specific extracellular ALA production rate under microaerobic-light cultivations (15.72-24.74 h and 0.222-0.299 h(-1), respectively) were better than those obtained under aerobic-dark cultivations (24.57-44.84 h and 0.103-0.215 h(-1), respectively). The biomass and the extracellular ALA yields of 39.66-56.25 gDCW/l/mol C, and 148.47-245.75 μM/mol C, respectively, under microaerobic-light cultivations were higher than of those obtained under aerobic-dark conditions. An enhancement of extracellular ALA production under aerobic-dark conditions revealed that the ALA yield was markedly increased 8-fold (48.36 μM) by the addition of 10mM succinate, 4.5mM glycine, and 15 mM levulinic acid (LA). By controlling dissolved oxygen (DO) and pH values, a maximum extracellular ALA yield of 66.38 μM was found. The degradation rate of ALA in the culture broth was closely related to the pH value.     

Sesamin modulation of lipid class and fatty acid profile in early juvenile teleost, Lates calcarifer, fed different dietary oils

Sesamin, a major sesame seed lignan, has diverse biological functions including the modulation of molecular actions in lipid metabolic pathways and reducing cholesterol levels. Vertebrates have different capacities to biosynthesize long-chain PUFA from dietary precursors and sesamin can enhance the biosynthesis of ALA to EPA and DHA in marine teleost. Early juvenile barramundi, Lates calcarifer, were fed for two weeks on diets rich in ALA or SDA derived from linseed or Echium plantagineum, respectively. Both diets contained phytosterols and less cholesterol compared with a standard fish oil-based diet. The growth rates were reduced in the animals receiving sesamin regardless of the dietary oil. However, the relative levels of n-3 LC-PUFA in total lipid, but not the phospholipid, increased in the whole body by up to 25% in animals fed on sesamin with ALA or SDA. Sesamin reduced the relative levels of triacylglycerols and increased polar lipid, and did not affect the relative composition of phospholipid subclasses or sterols. Sesamin is a potent modulator for LC-PUFA biosynthesis in animals, but probably will have more effective impact at advanced ages. By modulating certain lipid metabolic pathways, sesamin has probably disrupted the body growth and development of organs and tissues in early juvenile barramundi.     

Short-Chain Fatty Acids Produced by Ruminococcaceae Mediate α-Linolenic Acid Promote Intestinal Stem Cells Proliferation

Scope : The proliferation and differentiation of intestinal stem cells (ISCs) are the basis of intestinal renewal and regeneration, and gut microbiota plays an important role in it. Dietary nutrition has the effect of regulating the activity of ISCs; however, the regulation effect of α-linolenic acid (ALA) has seldom been reported. Methods and Results : After intervening mice with different doses of ALA for 30 days, it is found that ALA (0.5 g kg^?1) promotes small intestinal and villus growth by activating the Wnt/β-catenin signaling pathway to stimulate the proliferation of ISCs. Furthermore, ALA administration increases the abundance of the Ruminococcaceae and Prevotellaceae, and promotes the production of short-chain fatty acids (SCFAs). Subsequent fecal transplantation and antibiotic experiments demonstrate that ALA on the proliferation of ISCs are gut microbiota dependent, among them, the functional microorganism may be derived from Ruminococcaceae. Administration of isobutyrate shows a similar effect to ALA in terms of promoting ISCs proliferation. Furthermore, ALA mitigates 5-fluorouracil-induced intestinal mucosal damage by promoting ISCs proliferation. Conclusion : These results indicate that SCFAs produced by Ruminococcaceae mediate ALA promote ISCs proliferation by activating the Wnt/β-catenin signaling pathway, and suggest the possibility of ALA as a prebiotic agent for the prevention and treatment of intestinal mucositis.     

Antimicrobial activity of essential oil extracts of various onions (Allium cepa) and garlic (Allium sativum)

Antimicrobial activity of different concentrations (50, 100, 200, 300 and 500 ml/l) of essential oil extracts of three type of onions (green, yellow and red) and garlic against two bacteria, Staphylococcus aureus, Salmomella Enteritidis, and three fungi, Aspergillus niger, Penicillium cyclopium and Fusarium oxysporum, was investigated. The essential oil (EO) extracts of these Allium plants (garlic and onions) exhibited marked antibacterial activity, with garlic showing the highest inhibition and green onion the lowest. Comparatively, 50 and 100 ml/l concentrations of onions extracts were less inhibitory than 200, 300 and 500 ml/l concentrations. However, with garlic extract, high inhibitory activity was observed for all tested concentrations. S. aureus showed less sensitivity towards EO extracts inhibition, however S. Enteritidis was strongly inhibited by red onion and garlic extracts. The fungus F. oxysporum showed the lowest sensitivity towards EO extracts, whereas A. niger and P. cyclopium were significantly inhibited particularly at low concentrations. Conclusively, where seasoning is desired, essential oil extracts of onions and garlic can be used as natural antimicrobial additives for incorporating in various food products.     

ALA和GNT对苹果果皮中多酚、酶活及相关基因的影响

目的:探究5-氨基乙酰丙酸（5-Aminolevulinic acid,ALA）和金雀异黄素（Genistein,GNT）对苹果果皮总酚含量、花青苷、相关酶活性以及基因表达量的影响。方法:在\     

Healthy reduced-fat Bologna sausages enriched in ALA and DHA and stabilized with Melissa officinalis extract

Reduced-energy and reduced-fat Bologna products enriched with ω-3 polyunsaturated fatty acids were formulated by replacing the pork back-fat by an oil-in-water emulsion containing a mixture of linseed-algae oil stabilized with a lyophilized Melissa officinalis extract. Healthier composition and lipid profile was obtained: 85 kcal/100 g, 3.6% fat, 0.6 g ALA and 0.44 g DHA per 100 g of product and ω-6/ω-3 ratio of 0.4. Technological and sensory problems were not detected in the new formulations. Reformulation did not cause oxidation problems during 32 days of storage under refrigeration. The results suggest that it is possible to obtain reduced-fat Bologna-type sausages rich in ALA and DHA and stabilized with natural antioxidants, applying the appropriate technology without significant effects on the sensory quality, yielding interesting products from a nutritional point of view.     

Antifungal,antiaflatoxin and antioxidant potential of chemically characterized Boswellia carterii Birdw essential oil and its in vivo practical applicability in preservation of Piper nigrum L. fruits

The study explores the chemical profile, antimicrobial and antioxidant activity of Boswellia carterii essential oil (EO). The EO significantly inhibited growth and aflatoxin production by the food borne toxigenic strain of Aspergillus flavus at 1.75 μl/ml and 1.25 μl/ml respectively. It exhibited broad fungitoxic spectrum against 12 food borne moulds and also showed strong antioxidant activity, IC₅₀ value and % inhibition of linoleic acid peroxidation being 0.64 μl/ml and 51.68% respectively. The antifungal action of EO was observed in terms of reduction in ergosterol content of plasma membrane of A. flavus. As fumigant in food system in storage containers, the EO provided 65.38% protection against fungal deterioration of Piper nigrum. GC–MS results revealed 31 components of EO. The chemically characterized B. carterii EO may thus be recommended as plant based preservative in view of its antifungal, antiaflatoxigenic, antioxidant activity and efficacy in food system.     

Scavenging ability on ROS of alpha-lipoic acid (ALA)

The scavenging ability of alpha-lipoic acid (ALA) towards superoxide anions, hydroxyl radicals and hydrogen peroxide was evaluated by means of chemiluminescence (CL). In neutral or acid conditions, ALA could scavenge superoxide anions and its scavenging efficiency depended on its concentration. In neutral or alkaline conditions, the CL intensity of the reaction of ALA with hydroxyl radical (OH radicals) decreased after the first 10 min and then increased with time, suggesting that ALA could scavenge OH radicals at the beginning, but yielded unknown intermediate products that could lead to the increase of CL intensity at later stages. The increase of CL intensity in the reaction of hydrogen peroxide with ALA may also be due to these products.     

Effects of levulinic acid on 5-aminolevulinic acid production in heterotrophic cultures of Chlorella regularis YA-603

To investigate the effects of levulinic acid (LA) on extracellular 5-aminolevulinic acid (ALA) accumulation, a heterotrophic culture of Chlorella regularis YA-603 in basal medium containing 0 to 60 mM of LA was carried out. It was found that the extracellular and total ALA concentrations increased, while the chlorophyll (CHL) concentration was the same above initial LA concentrations of 30 mM, with an increasing initial LA concentration up to 50 mM. In the presence of an initial LA concentration of 60 mM, however, the specific growth rate decreased markedly. This suggested that excessive LA exerted a negative effect on ALA production because it also directly affected cellular growth. The relationship between the initial LA and total ALA concentrations mentioned above indicates that LA could promote the ALA-producing activity. Kinetic analysis revealed that an LA concentration of between 30 to 50 mM in the culture broth gave the maximum specific production rate of ALA ((q(ALA))max). When LA was added repeatedly to maintain this optimum range of LA concentration, (q(ALA))max could be maintained at a relatively high level for a longer period, and the maximum concentration of ALA reached 3.86 mM.     

Formation of vinylphenolic pyranoanthocyanins by Saccharomyces cerevisiae and Pichia guillermondii in red wines produced following different fermentation strategies

The strains of two species of yeast, Saccharomyces cerevisiae and Pichia guillermondii, both with high hydroxycinnamate decarboxylase (HCDC) activity (56% and 90% respectively), were used in the fermentation of musts enriched with grape anthocyanins, to favour the formation of highly stable vinylphenolic pyranoanthocyanin pigments. The different strains were used to ferment the must separately, simultaneously, or sequentially, the latter involving an initial period using the yeast with the greatest HCDC activity (P. guillermondii). The must was made from concentrated grape juice diluted to 220 g/l of sugar, and enriched with grape anthocyanins to 100 mg/l and with p-coumaric acid to 120 mg/l. The pH was fixed to 3.5. All 50 ml micro-fermentations were done in triplicate. The development of anthocyanin-3-O-glucoside precursors, the decarboxylation of p-coumaric acid, and the formation of 4-vinylphenol and vinylphenolic pyranoanthocyanin derivatives were studied during the fermentation. The fermentation strategy used and the yeast HCDC activity significantly influenced the formation of vinylphenolic pyranoanthocyanins. The latter molecules were separated, identified, and quantified using high performance liquid chromatograph with diode array detection and electrospray-mass spectrometry (HPLC-DAD-ESI/MS). The volatile compounds profile was screened during fermentation using gas cromatogrphy-flame ionisation detection (GC-FID), in order to detect and quantify the main molecules. The best results were reached with the sequential fermentation (3.74 mg/l of malvidin-3-O-glucoside-4-vinylphenol). This work shows that during mixed or sequential fermentations carried out with non-Saccharomyces or highly fermentative Saccharomyces strains, with high HCDC activity, the content of stable pigments can be increased without sensorial modifications.     

Survival of three Bifidobacterium animalis subsp. lactis strains is related to trans-vaccenic and α-linolenic acids contents in organic fermented milks

This study aims at relating the survival at 4 °C for 28 days in organic and conventional fermented milks of three strains of Bifidobacterium animalis subsp. lactis (BB12, B94 and BL04), in co-culture with Streptococcus thermophilus TA040 and Lactobacillus bulgaricus LB340, to milk fatty acids profile. Cultivability after 28 days of cold storage was improved in organic fermented milks as compared to conventional products, with slight differences among strains. In addition, the poly-unsaturated fatty acids fraction was higher in organic products, as well as the relative trans-vaccenic (TVA) and α-linolenic (ALA) fatty acids contents that were respectively 1.7 and 2.4 times higher in organic than in conventional fermented milks. From these results, it was concluded that elevated levels of TVA and ALA, together with a lower ratio between linoleic acid and α-linolenic acid, as found in organic products, improved the survival of the bifidobacteria during chilled storage.     

Comparative chemical composition,antioxidant and hypoglycaemic activities of Juniperus oxycedrus ssp. oxycedrus L. berry and wood oils from Lebanon

Juniper (Juniperus oxycedrus) is used in European cuisine for its distinguishing flavour. J. oxycedrus ssp. oxycedrus berry and wood essential oils were tentatively identified by GC and GC/MS. Fifty compounds were identified in the berry oil and 23 compounds were identified in the wood oil. The J. oxycedrus ssp. oxycedrus berry oil was characterised by high contents of α-pinene (27.4%) and β-myrcene (18.9%). Other important compounds were α-phellandrene (7.1%), limonene (6.7%), epi-bicyclosesquiphellandrene (2.3%) and δ-cadinene (2.2%) while, in the wood oil, δ-cadinene (14.5%) is a major main component, together with cis-thujopsene (9.2%) and α-muurolene (4.9%). In vitro evaluation of antioxidant activity by the DPPH method showed a significant activity for both oils with IC₅₀ values of 1.45 μl/ml for wood and 7.42 μl/ml for berries. Hypoglycaemic activity was investigated through the inhibition of α-amylase. The results revealed that oil obtained by hydrodistillation from J. oxycedrus ssp. oxycedrus wood exhibits an interesting activity with IC₅₀ of 3.49 μl/ml.     

n-3多不饱和脂肪酸对疾病的预防与治疗作用

n-3多不饱和脂肪酸主要源于亚麻籽、胡桃仁、大豆以及海洋生物。增加n-3多不饱和脂肪酸摄取量可以促进视网膜、大脑和神经系统发育。n-3多不饱和脂肪酸通过各种途径降低人体心血管疾病和炎症的发生,降低糖尿病患者血清低密度脂蛋白胆固醇(LDL-C)和甘油三酯(TG)水平。膳食中增加n-3多不饱和脂肪酸的含量可以对心血管疾病、糖尿病、炎症等患者有辅助治疗效果;n-3多不饱和脂肪酸可以作用于神经细胞,对注意力不集中、抑郁症、精神分裂症有一定的疗效。n-3多不饱和脂肪酸可抑制体外培养的乳腺、前列腺和结肠癌细胞增生,促进细胞凋亡。