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1.
Poly(ε-l-lysine) (ε-PL) is a naturally occurring poly(amino acid) characterized by a unique structure linking ε-amino and carboxyl groups of l-lysine. Due to its various functions and its biodegradability and non-toxicity, the ε-PL polymer has attracted increasing attention in recent years. ε-PL is frequently found in various strains of Streptomyces sp. This review gives an up-to-date overview regarding the biosynthesis of ε-PL focussing mainly on results obtained from ten newly isolated producer strains, using the two-stage culture method of cell growth and ε-PL production cultures. The production of nearly monodispersed ε-PL is covered together with the development of ε-PL specific hydrolases and the release of synthesized ε-PL into the culture broth. From these results, coupled with the termination of polymerization through nucleophilic chain transfer, the biosynthetic mechanism of the polymer is discussed.  相似文献   

2.
ε-Poly-l-lysine (ε-PL)—a natural food preservative with wide antimicrobial activity and high food safety—is increasingly attracting widespread attention. However, the high cost of raw materials severely impairs its economy and utilization. In this study, agro-industrial by-products, i.e., fish meal coupled with corn steep liquor, were employed as alternative organic nitrogen sources for industrial ε-PL production by Streptomyces sp. M-Z18. An economical medium was then developed by using an artificial neural network. Amino acids analyses showed that the improved medium was rich in glutamate, arginine, lysine and aspartate, which not only elevated the acid tolerance capability of the mycelia but also enhanced cell growth and ε-PL production. Subsequently, a cost-effective and efficient strategy for ε-PL production was established on fermenter scale, based on the improved medium and two-stage pH control. Notably, ε-PL production and productivity reached 35.24 g/L and 4.85 g/L day in fed-batch fermentation. Further profit assessment at the 10 m3 scale indicated that application of this strategy resulted in a net profit increase of 9,057 USD. Therefore, the proposed strategy has great potential for industrial production of ε-PL.  相似文献   

3.
Glycoside hydrolases form hyperthermophilic archaea are interesting model systems for the study of catalysis at high temperatures and, at the moment, their detailed enzymological characterization is the only approach to define their role in vivo. Family 29 of glycoside hydrolases classification groups α-l-fucosidases involved in a variety of biological events in Bacteria and Eukarya. In Archaea the first α-l-fucosidase was identified in Sulfolobus solfataricus as interrupted gene expressed by programmed −1 frameshifting. In this review, we describe the identification of the catalytic residues of the archaeal enzyme, by means of the chemical rescue strategy. The intrinsic stability of the hyperthermophilic enzyme allowed the use of this method, which resulted of general applicability for β and α glycoside hydrolases. In addition, the presence in the active site of the archaeal enzyme of a triad of catalytic residues is a rather uncommon feature among the glycoside hydrolases and suggested that in family 29 slightly different catalytic machineries coexist.  相似文献   

4.
Liu S  Wu Q  Zhang J  Mo S 《Biotechnology letters》2011,33(8):1581-1585
Resin-based, in situ product removal (ISPR) was used to increase production of ε-poly-l-lysine (PL) by Streptomyces sp. GIM8. D152 resin was selected over Amberlite IRC-50, Amberlite IRC-76 and Amberlite IR-120 to develop ISPR using adsorption capacity and desorption ratio as bases. The yield of PL in response to external PL was unaffected in shake-flask culture; however, the production of PL increased to 2.9 from 0.8 g l−1 shake-flasks using ISPR. In a 5 l fermentor, 23.4 g PL l−1 was achieved compared to 3.76 g PL l−1, in the controls by attaching two bags of D152 resin to the probes and baffles of the fermentor.  相似文献   

5.
Poly(ε-l-lysine) (ε-PL) is a naturally-occurring l-lysine homopolymer having antimicrobial activity. A newly-isolated strain of Streptomyces aureofaciens produced a short chain length ε-PL consisting of 5–20 residues at the highest production level of 4.5 g l–1. This ε-PL had different spectra in terms of antimicrobial activity from the ε-PL that is now used as a food preservative. The high productivity was based on multiple metabolic pathways for l-lysine synthesis, and a great flux from l-lysine to ε-PL. The usefulness of this new ε-PL and its producing strain was discussed.  相似文献   

6.
Tao F  Luo Y  Huang Q  Liu Y  Li B  Zhang G 《Amino acids》2009,37(4):603-607
l-β-Haloalanines are physiologically active unnatural amino acids and they are useful intermediates for the synthesis of natural and unnatural amino acids, S-linked glycopeptides, and lanthionines. In general l-β-haloalanines were prepared predominantly from l-serine via functional group transformation. Here we reported an alternative approach for the preparation of l-β-haloalanines via halogenation of protected l-cysteine esters which was obtained from l-cysteine or l-cystine, respectively. The mercapto group of protected l-cysteine esters was efficiently transformed to halo groups by triphenylphosphine/N-halosuccinimides. It has been proved to be a versatile desulfurization strategy via this functional group transformation.  相似文献   

7.
Poly (β-l-malic acid) (PMLA) is a water-soluble polyester with many attractive properties in chemical industry and medicine development. However, the low titer of PMLA in the available producer strains limits further industrialization efforts and restricts its many potential applications. In order to solve this problem, a new strain with the distinguished high productivity of PMLA was isolated from fresh plants samples. It was characterized as the candidate of Aureobasidium pullulans based on the morphology and phylogenetic analyses of the internal transcribed spacer sequences. After the optimization of culture conditions, the highest PMLA concentration (62.27 g l−1) could be achieved in the shake flask scale. In addition, the contribution of the carbon flux to exopolysaccharide (EPS) and PMLA could be regulated by the addition of CaCO3 in the medium. This high-level fermentation process was further scaled up in the 10 l benchtop fermentor with a high PMLA concentration (57.2 g l−1) and productivity (0.35 g l−1 h−1), which are the highest level in all the literature. Finally, the suitable acid hydrolysis conditions of PMLA were also investigated with regard to the production of l-malic acid, and the kinetics of PMLA acid hydrolysis was modeled to simulate the whole degradation process. The present work paved the road to produce this multifunctional biomaterial (PMLA) at industrial scale and promised one alternative method to produce l-malic acid in the future.  相似文献   

8.
α-l-Rhamnosidase from Aspergillus terreus was covalently immobilized on the following ferromagnetic supports: polyethylene terephthalate (Dacron-hydrazide), polysiloxane/polyvinyl alcohol (POS/PVA), and chitosan. The powdered supports were magnetized by thermal coprecipitation method using ferric and ferrous chlorides, and the immobilization was carried out via glutaraldehyde. The activity of the Dacron-hydrazide (0.53 nkat/μg of protein) and POS/PVA (0.59 nkat/μg of protein) immobilized enzyme was significantly higher than that found for the chitosan derivative (0.06 nkat/μg of protein). The activity–pH and activity–temperature profiles for all immobilized enzymes did not show difference compared to the free enzyme, except the chitosan derivative that presented higher maximum temperature at 65 °C. The Dacron-hydrazide derivative thermal stability showed a similar behavior of the free enzyme in the temperature range of 40–70 °C. The POS/PVA and chitosan derivatives were stable up to 60 °C, but were completely inactivated at 70 °C. The activity of the preparations did not appreciably decrease after ten successive reuses. Apparent K m of α-l-rhamnosidase immobilized on magnetized Dacron-hydrazide (1.05 ± 0.22 mM), POS/PVA (0.57 ± 0.09 mM), and chitosan (1.78 ± 0.24 mM) were higher than that estimated for the soluble enzyme (0.30 ± 0.03 mM). The Dacron-hydrazide enzyme derivative showed better performance than the free enzyme to hydrolyze 0.3% narigin (91% and 73% after 1 h, respectively) and synthesize rhamnosides (0.116 and 0.014 mg narirutin after 1 h, respectively).  相似文献   

9.
A glycosyl hydrolase family 54 (GH54) α-l-arabinofuranosidase gene (abfA) of Aureobasidium pullulans was amplified by polymerase chain reaction from genomic DNA and a 498-amino-acid open reading frame deduced from the DNA sequence. Modeling of the highly conserved A. pullulans AbfA protein sequence on the crystal structure of Aspergillus kawachii AkabfB showed that the catalytic amino acid arrangement and overall structure were highly similar including the N-terminal catalytic and C-terminal arabinose binding domains. The abfA gene was expressed in Saccharomyces cerevisiae, and the heterologous enzyme was purified. The protein was monomeric, migrating at 49 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and eluting at 36 kDa upon gel filtration. AbfA showed maximal activity at 55°C and between pH 3.5 and pH 4. The enzyme had a K m value for p-nitrophenyl-α-l-arabinofuranoside of 3.7 mM and a V max of 34.8 μmol min−1 mg protein−1. Arabinose acted as a noncompetitive inhibitor with a K i of 38.4 mM. The enzyme released arabinose from maize fiber, oat spelt arabinoxylan, and wheat arabinoxylan, but not from larch wood arabinogalactan or α-1,5-debranched arabinan. AbfA displayed low activity against α-1,5-l-arabino-oligosaccharides. The enzyme acted synergistically with endo-β-1,4-xylanase in the breakdown of wheat arabinoxylan. Binding of AbfA to xylan from several sources confirmed the presence of a functional carbohydrate-binding module. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

10.
Streptomyces albulus NBRC14147 produces ɛ-poly-l-lysine (ɛ-PL), which is an amino acid homopolymer antibiotic. Despite the commercial importance of ɛ-PL, limited information is available regarding its biosynthesis; the l-lysine molecule is directly utilized for ɛ-PL biosynthesis. In most bacteria, l-lysine is biosynthesized by an aspartate pathway. Aspartokinase (Ask), which is the first enzyme in this pathway, is subject to complex regulation such as through feedback inhibition by the end-product amino acids such as l-lysine and/or l-threonine. S. albulus NBRC14147 can produce a large amount of ɛ-PL (1–3 g/l). We therefore suspected that Ask(s) of S. albulus could be resistant to feedback inhibition to provide sufficient l-lysine for ɛ-PL biosynthesis. To address this hypothesis, in this study, we cloned the ask gene from S. albulus and investigated the feedback inhibition of its gene product. As predicted, we revealed the feedback resistance of the Ask; more than 20% relative activity of Ask was detected in the assay mixture even with extremely high concentrations of l-lysine and l-threonine (100 mM each). We further constructed a mutated ask gene for which the gene product Ask (M68V) is almost fully resistant to feedback inhibition. The homologous expression of Ask (M68V) further demonstrated the increase in ɛ-PL productivity.  相似文献   

11.
The δ-(l-α-aminoadipyl)-l-cysteinyl-d-valine (ACV) tripeptide is the first dedicated intermediate in the biosynthetic pathway leading to the penicillin and cephalosporin classes of β-lactam natural products in bacteria and fungi. It is synthesized nonribosomally by the ACV synthetase (ACVS) enzyme, which has been purified and partially characterized from many sources. Due to its large size and instability, many details regarding the reaction mechanism of ACVS are still not fully understood. In this review we discuss the chronology and associated methodology that led to the discovery of ACVS, some of the main findings regarding its activities, and some recent/current studies being conducted on the enzyme. In addition, we conclude with perspectives on what can be done to increase our understating of this very important protein in the future.  相似文献   

12.
Actinomycetes are the most important microorganisms for the industrial production of secondary metabolites with antimicrobial and anticancer properties. However, they have not been implicated in biorefineries. Here, we study the ability of the ε-poly-l-lysine producing Streptomyces albulus BCRC 11814 to utilize biodiesel-derived crude glycerol. S. albulus was cultured in a mineral medium supplemented with up to 10% w/v sodium chloride or potassium chloride, and with crude glycerol as the sole carbohydrate source. Under these conditions, the strain produced 0.1 g ε-poly-l-lysine per 1 g of biomass. RNA sequencing revealed upregulation of the ectoine biosynthetic pathway of S. albulus, which provides proof of halotolerance. S. albulus has several silent secondary metabolite biosynthetic clusters predicted within the genome. Based on the results, we conclude that S. albulus BCRC 11814 is a halotolerant microorganism capable of utilizing biodiesel-derived crude glycerol better than other actinomycetes included in the present study. S. albulus has the potential to be established as microbial platform production host for a range of high-value biological products.  相似文献   

13.
β-N-Methylamino-l-alanine (BMAA), a non-proteinogenic amino acid, has been detected in a range of cyanobacteria, including terrestrial, aquatic, free living and endosymbiotic species. The widespread occurrence of cyanobacteria in the environment raises concerns regarding the ecological and toxicological impact of BMAA, and consequently, studies have focussed extensively on the toxicity and environmental impact of BMAA, while no research has addressed the ecophysiological or metabolic role of the compound in cyanobacteria. In this study, both the uptake of exogenous BMAA by and the effect of exogenous BMAA on the growth of Synechocystis PCC6803 were investigated. BMAA was rapidly taken up by the non-diazotrophic cyanobacterium Synechocystis PCC6803 in a concentration dependent manner. The presence of exogenous BMAA resulted in a substantial and concentration-dependent decrease in cell growth and the substantial loss of photosynthetic pigmentation. Similar effects were seen in the presence of the non-proteinogenic amino acid, 2,4-diaminobutyric acid but to a lesser degree than that of BMAA. The effects were reversed when light was decreased from 16 to 10 μmol m−2 s−1. Control cultures grown in the presence of l-arginine, l-asparagine, l-glutamate and glycine showed normal or slightly increased growth with no change in pigmentation. The decrease in growth rate coupled to bleaching indicates that BMAA may induce chlorosis in the presence of adequate photosynthetic radiation suggesting a connection between BMAA and the induction of conditions, such as nitrogen or sulphur depletion, that result in growth arrest and the induction of chlorosis.  相似文献   

14.
To improve the efficiency of ε-poly-l-lysine (ε-PL) production by Streptomyces sp. M-Z18, batch and fed-batch fermentations with glucose and glycerol (co-fermentations) were performed. The batch fermentations showed that the initial ratio of glucose to glycerol plays an important role in glucose/glycerol co-fermentation. The optimal glucose/glycerol weight ratio was 30/30; this resulted in a maximum ε-PL productivity of 5.26 g/L/d. Glucose and glycerol were consumed synergistically during the co-fermentation process, and the length of time during which the substrate was exhausted was significantly shortened compared with the single carbon source fermentation. Under optimized conditions, fed-batch fermentations with glucose and glycerol as a mixed carbon source achieved maximum ε-PL concentration and productivity values of 35.14 g/L and 4.85 g/L/d, respectively. These values were respectively 1.43- and 1.39-, and 1.17- and 1.16-folds higher than those obtained from fermentations with glucose and glycerol as single carbon sources. The present study is the first to suggest that glucose/glycerol co-fermentation may be an efficient strategy for ε-PL production by Streptomyces sp. M-Z18.  相似文献   

15.
Penicillium ulaiense is a post-harvest pathogenic fungus that attacks citrus fruits. The objective of this work was to study this microorganism as an α-l-rhamnosidase producer and to characterize it from P. ulaiense. The enzyme under study is used for different applications in food and beverage industries. α-l-Rhamnosidase was produced in a stirred-batch reactor using rhamnose as the main carbon source. The kinetic parameters for the growth of the fungi and for the enzyme production were calculated from the experimental values. A method for partial purification, including (NH4)2SO4 precipitation, incubation at pH 12 and DEAE-sepharose chromatography yielded an enzyme with very low β-glucosidase activity. The pH and temperature optima were 5.0 and 60°C, respectively. The Michaelis–Menten constants for the hydrolysis of p-nitrophenyl-α-l-rhamnoside were V max = 26 ± 4 IU ml−1 and K m  = 11 ± 2 mM. The enzyme showed good thermostability up to 60°C and good operational stability in white wine. Co2+ affected positively the activity; EDTA, Mn2+, Mg2+, dithiotreitol and Cu2+ reduced the activity by different amounts, and Hg2+ completely inhibited the enzyme. The enzyme showed more activity on p-nitrophenyl-α-l-rhamnoside than on naringin. According to these results, this enzyme has potential for use in the food and pharmacy industries since P. ulaiense does not produce mycotoxins.  相似文献   

16.
ε-poly-l-lysine (ε-PL) is a homo-poly-amino acid of l-lysine which is used as a safe food preservative. The productivity of ε-PL in currently reported wild type strains is low. This study was aimed at finding novel ε-PL producing strains with higher productivity and new fermentative characters. An improved detection method was employed using methylene blue as an ε-PL secretion indicator. 137 strains forming transparent circles were isolated. The best one was identified as Streptomyces griseofuscus according to the morphological characteristics and the comparison of internal transcribed spacer (ITS) ribosomal DNA (rDNA) gene sequences. The fermentative behavior of S. griseofuscus was investigated, and the ε-PL production was enhanced to 2.3 g/L in 5-L bioreactor by a pH control strategy. The yield of ε-PL reached 7.5 g/L in the fed-batch process. Compared with the reported wild type strains, S. griseofuscus produced relatively higher amounts of ε-PL, and might be a promising Streptomyces for ε-PL production.  相似文献   

17.
A recombinant putative glycoside hydrolase from Caldicellulosiruptor saccharolyticus was purified with a specific activity of 12 U mg−1 by heat treatment and His-Trap affinity chromatography, and identified as a single 56 kDa band upon SDS-PAGE. The native enzyme is a dimer with a molecular mass of 112 kDa as determined by gel filtration. The enzyme exhibited its highest activity when debranched arabinan (1,5-α-l-arabinan) was used as the substrate, demonstrating that the enzyme was an endo-1,5-α-l-arabinanase. The K m, k cat, and k cat/K m values were 18 mg ml−1, 50 s−1, and a 2.8 mg ml−1 s−1, respectively. Maximum enzyme activity was at pH 6.5 and 75°C. The half-lives of the enzyme at 65, 70 and 75°C were 2440, 254 and 93 h, respectively, indicating that it is the most thermostable of the known endo-1,5-α-l-arabinanases.  相似文献   

18.
Flax seed mucilage (FM) contains a mixture of highly doubly substituted arabinoxylan as well as rhamnogalacturonan I with unusual side group substitutions. Treatment of FM with a GH11 Bacillus subtilis XynA endo 1,4-β-xylanase (BsX) gave limited formation of reducing ends but when BsX and FM were incubated together on different wheat arabinoxylan substrates and birchwood xylan, significant amounts of xylose were released. Moreover, arabinose was released from both water-extractable and water-unextractable wheat arabinoxylan. Since no xylose or arabinose was released by BsX addition alone on these substrates, nor without FM or BsX addition, the results indicate the presence of endogenous β-d-xylosidase and α-l-arabinofuranosidase activities in FM. FM also exhibited activity on both p-nitrophenyl α-l-arabinofuranoside (pNPA) and p-nitrophenyl β-d-xylopyranoside (pNPX). Based on K M values, the FM enzyme activities had a higher affinity for pNPX (K M 2 mM) than for pNPA (K M 20 mM).  相似文献   

19.
Two strains PB196T and PB62T of Gram-negative, non-motile, and non-spore-forming bacteria, were isolated from soil in South Korea and characterized to determine their taxonomic positions. 16S rRNA gene sequence analysis showed that the two strains belonged to the genus Sphingomonas. The highest degree of sequence similarity of strain PB196T was found with PB62T (98.9%), Sphingomonas humi PB323T (98.9%), Sphingomonas kaistensis PB56T (98.2%), and Sphingomonas astaxanthinifaciens TDMA-17T (98.0%). The highest degree of sequence similarity of strain PB62T was found with Sphingomonas humi PB323T (98.8%), Sphingomonas astaxanthinifaciens TDMA-17T (98.2%), and Sphingomonas kaistensis PB56T (98.1%). Chemotaxonomic data revealed that they possessed ubiquinone-10 (Q-10) as common in the genus Sphingomonas, that the predominant fatty acids were summed feature 7 (C18:1 ω7c/ω9t/ω12t), summed feature 4 (C16:1 ω7c/C15:0 iso 2OH), C16:0, and C17:1 ω6c, and that they contained sphingoglycolipid, phosphatidylglycerol (PG), and phosphatidyle-thanolamine (PE) in common but they showed difference for diphosphatidylglycerol (DPG). Based on these data, PB196T (=KCTC 12339T =JCM 16604T) and PB62T (=KCTC 12336T =JCM 16605T =KEMB 9004-005T) should be classified as type strains of two novel species, for which the names Sphingomonas rosea sp. nov. and Sphingomonas swuensis sp. nov. are proposed, respectively.  相似文献   

20.
A bacterial strain, MAK-2, was isolated as a producer of α-l-rhamnosidase from a soil sample of Dehradoon, India. The strain was identified based on morphology, physiological tests and 16S rDNA analysis. The phylogenetic analysis based on the 16S rDNA sequence, identified the isolate as Staphylococcus xylosus, a non-pathogenic member of CNS (coagulase-negative staphylococci) family. The strain was capable of producing α-l-rhamnosidase by hydrolysing flavonoids thus confirming potential application in the citrus-processing industry.  相似文献   

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