Streptomyces polyrhachii sp. nov., a novel actinomycete isolated from an edible Chinese black ant (Polyrhachis vicina Roger)

A novel actinomycete, designated strain NEAU-ycm1^T, was isolated from an edible Chinese black ant (Polyrhachis vicina Roger) and characterized with a polyphasic approach. The organism was found to have morphological and chemotaxonomic characteristics typical of streptomycetes. Phylogenetic analysis based on the almost complete 16S rRNA gene sequence show that the novel isolate belongs to the genus Streptomyces and forms a separate subclade. The closest phylogenetic relatives were identified as the type strains of Streptomyces intermedius NBRC 13049^T (97.74 %), Streptomyces aureoverticillatus NRRL B-3326^T (97.69 %), Streptomyces rutgersensis NBRC 12819^T (97.68 %), Streptomyces gougerotii NBRC 3198^T (97.68 %) and Streptomyces diastaticus subsp. diastaticus NBRC 3714^T (97.68 %). Similarities to other type strains of the genus Streptomyces were lower than 97.55 %. A comparison between strain NEAU-ycm1^T and the closest related Streptomyces type strains revealed that it is different from them in morphological, physiological and biochemical characteristics. Therefore, it is proposed that NEAU-ycm1^T (=CGMCC 4.7094^T = DSM 42102^T) represents a novel species of the genus of Streptomyces, for which the name Streptomyces polyrhachii sp. nov. is proposed.     

Streptomyces fukangensis sp. nov., a novel alkaliphilic actinomycete isolated from a saline-alkaline soil

An alkaliphilic actinobacterium, designated EGI 80050^T, was isolated from a desert soil sample of Xinjiang, north-west China, and characterized by a polyphasic approach. The isolate was observed to produce purple orange-yellow aerial mycelium and dark orange-yellow substrate mycelium on yeast extract-malt extract agar medium. Whole-cell hydrolysates of strain EGI 80050^T were found to contain ll-diaminopimelic acid as the diagnostic diamino acid, and galactose, glucose, rhamnose and mannose as the main sugars. The major fatty acids identified were C_16:0-iso (36.8 %), C_15:0-anteiso (17.3 %), 15:0-iso (13.2 %) and 14:0-iso (10.5 %). The predominant menaquinones detected were MK-9(H₆) and MK-9(H₈), while the characteristic polar lipids were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides, phosphatidylmethylethanolamine and three unknown phospholipids. The G+C content of the genomic DNA was determined to be 67.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequences affiliated the strain EGI 80050^T to the genus Streptomyces. Levels of 16 rRNA gene sequence similarities between strain EGI 80050^T and Streptomyces candidus NRRL ISP-5141^T, Streptomyces cremeus NBRC 12760^T, Streptomyces spiroverticillatus NBRC 12821^T, Streptomyces violaceorectus NBRC 13102^T, Streptomyces cinereoruber subsp. cinereoruber NBRC 12756^T were 96.7, 96.6, 96.6, 96.6 and 96.6 %, respectively. Based on the phenotypic, chemotaxonomic and phylogenetic data, strain EGI 80050^T is considered to represent a novel species of the genus Streptomyces, for which the name Streptomyces fukangensis sp. nov. (type strain EGI 80050^T = BCRC 16945^T = JCM 19127^T) is proposed.     

Streptomyces jiujiangensis sp. nov., isolated from soil in South China

An actinomycete capable of lysing cyanobacteria, strain JXJ 0074^T, was isolated from a soil sample collected from Jiangxi province, south China, and characterized by using polyphasic taxonomy. The new isolate showed morphological and chemotaxonomic properties typical of members of the genus Streptomyces. Phylogenetic analysis of the near-complete 16S rRNA gene sequence indicated that strain JXJ 0074^T should be affiliated to the genus Streptomyces and exhibited highest similarities to Streptomyces shenzhenensis DSM 42034^T (98.99 %) and Streptomyces lucensis NBRC 13056^T (98.60 %), while the similarities to other members of the genus are lower than 98.22 % similarity. However, the DNA–DNA hybridization values between strain JXJ 0074^T and S. shenzhenensis DSM 42034^T or S. lucensis NBRC 13056^T were 46.2 ± 2.6 and 32.6 ± 3.1 %, respectively. Thus, on the basis of the polyphasic data, strain JXJ 0074^T represents a novel species of the genus Streptomyces, for which the name Streptomyces jiujiangensis sp. nov. is proposed. The type strain is JXJ 0074^T (= BCRC 16953^T = KCTC 29262^T).     

Streptomyces erringtonii sp. nov. and Streptomyces kaempferi sp. nov., isolated from a hay meadow soil

Two filamentous actinomycetes isolated from a hay meadow soil were provisionally assigned to the genus Streptomyces based on morphological features. The isolates were found to have chemical and morphological properties typical of the genus Streptomyces and formed distinct phyletic lines in the 16S rRNA gene tree. Isolate I36^T was most closely related to Streptomyces glauciniger NBRC 100913^T and isolate I37^T to Streptomyces mirabilis NBRC 13450^T. Low DNA:DNA relatedness values were recorded between each of the isolates and their closest phylogenetic neighbour. The isolates were also distinguished from their nearest phylogenetic neighbour, and from one another, using a combination of phenotypic properties. These data indicate that the isolates should be recognised as new species in the genus Streptomyces. The names proposed for these new taxa are Streptomyces erringtonii sp. nov. and Streptomyces kaempferi sp. nov. with isolate I36^T (=CGMCC 4.7016^T = KACC 15424^T) and isolate I37^T (=CGMCC 4.7020^T = KACC 15428^T) as the respective type strains.     

Streptomyces canchipurensis sp. nov., isolated from a limestone habitat

Hundung Limestone habitat, Manipur, India is an unexplored site for microbial diversity studies. Using polyphasic taxonomy, a Streptomyces strain, MBRL 172^T, has been characterized. The strain was found to show highest 16S rRNA gene sequence similarity with Streptomyces coeruleofuscus NBRC 12757^T (99.2 %). The DNA relatedness between MBRL 172^T and S. coeruleofuscus NBRC 12757^T, and between MBRL 172^T and Streptomyces nogalater NBRC 13445^T, were 36.8 ± 4.4 and 52.5 ± 2.7 %, respectively. Strain MBRL 172^T was found to contain ll-diaminopimelic acid as the diagnostic diamino acid and glucose, mannose and xylose as the major sugars in whole cell hydrolysates. The polar lipids in the cell membrane were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositolmannoside. The predominant menaquinones detected were MK-9(H₆) and MK-9(H₈). The cellular fatty acids identified were mainly saturated fatty acids: anteiso-C_15:0, iso-C_16:0 and iso-C_15:0. Based on differences in the biochemical and molecular characteristics from its closest relatives, the strain can be proposed to represent a novel taxon in the genus Streptomyces, for which the name Streptomyces canchipurensis is proposed, with the type strain MBRL 172^T (=JCM 17575^T = KCTC 29105^T).     

Molecular and culture dependent characterization of endolithic bacteria in two beach sand samples and description of Rhizobium endolithicum sp. nov.

The taxonomic position of a streptomycete isolated from a potato tubercle was determined by using a polyphasic approach. The organism had chemotaxonomic and morphological properties consistent with its classification in the genus Streptomyces and formed a distinct phyletic line in the Streptomyces 16S rRNA gene tree. It was found to be closely related to Streptomyces celluloflavus NRRL B-2493^T (99.4 % 16S rRNA gene similarity) and shared a 99.0 % 16S rRNA gene similarity value with Streptomyces albolongus NRRL B-3604^T and Streptomyces cavourensis subsp. cavourensis NBRC 13026^T; low levels of DNA–DNA relatedness with these organisms showed that the isolate belonged to a distinct genomic species. The isolate was distinguished readily from the type strains of these species using a combination of morphological and other phenotypic properties. On the basis of these results, it is proposed that isolate ASBV-1^T (= CBMAI 1465^T = CCMA 894^T = NRRL B-24922^T) be classified as the type strain of Streptomyces araujoniae sp. nov.     

Enhancement of ε-poly-l-lysine production coupled with precursor l-lysine feeding in glucose–glycerol co-fermentation by Streptomyces sp. M-Z18

ε-Poly-l-lysine (ε-PL), one of the only two homo-poly amino acids known in nature, is used as a preservative. In this study, strategies of feeding precursor l-lysine into 5 L laboratory scale fermenters, including optimization of l-lysine concentration and time, was investigated to optimize the production of ε-PL by Streptomyces sp. M-Z18. The optimized strategy was then used in ε-PL fed-batch fermentation in which glucose and glycerol served as mixed carbon sources. In this way, a novel ε-PL production strategy involving precursor l-lysine coupled with glucose–glycerol co-fermentation was developed. Under optimal conditions, ε-PL production reached 37.6 g/l, which was 6.2 % greater than in a previous study in which glucose and glycerol co-fermentation was performed without added l-lysine (35.14 g/l). To the best of our knowledge, this is the first report of the enhancement of ε-PL production through l-lysine feeding to evaluate the use of fermenters. Meanwhile, the role of l-lysine in the promotion of ε-PL production, participating ε-PL synthesis as a whole, was first determined using the l-[U–¹³C] lysine labeling method. It has been suggested that the bottleneck of ε-PL synthesis in Streptomyces sp. M-Z18 is in the biosynthesis of precursor l-lysine. The information obtained in the present work may facilitate strain improvement and efficient large-scale ε-PL production.     

Genetic engineering of Escherichia coli to enhance production of l-tryptophan

Reducing the accumulation of acetate in Escherichia coli cultures can decrease carbon efflux as by-products and reduce acetate toxicity, and therefore enable high cell density cultivation. The concentration of intracellular amino acids can be decreased by genetic modifications of the corresponding amino acid transport systems. This can increase the levels of amino acids in the fermentation broth by decreasing the feedback inhibition on the corresponding biosynthetic pathways. Here, the effects of genetic manipulation of phosphate acetyltransferase (pta), high affinity tryptophan transporter (mtr) and aromatic amino acid exporter (yddG) on l-tryptophan production were investigated. The pta mutants accumulated less acetate and showed higher capacity for producing l-tryptophan as compared with the parental strain. The strains lacking mtr, or overexpressed yddG, or with the both mtr knockout and yddG overexpression, accumulated lower concentrations of intracellular tryptophan but higher production of extracellular l-tryptophan. In the l-tryptohan fed-batch fermentation of an E. coli derived from TRTH0709/pMEL03 having deletion of pta-mtr and overexpression of yddG in a 30-L fermentor, the maximum concentration of l-tryptophan (48.68 g/L) was obtained, which represented a 15.96 % increase as compared with the parental strain. Acetate accumulated to a concentration of 0.95 g/L. The intracellular concentration of l-tryptophan was low, and the glucose conversion rate reached a high level of 21.87 %, which was increased by 15.53 % as compared with the parent strain.     

Bacteria isolated from soils of the western Amazon and from rehabilitated bauxite-mining areas have potential as plant growth promoters

Several processes that promote plant growth were investigated in endophytic and symbiotic bacteria isolated from cowpea and siratro nodules and also in bacterial strains recommended for the inoculation of cowpea beans. The processes verified in 31 strains were: antagonism against phytopathogenic fungi, free-living biological nitrogen fixation, solubilization of insoluble phosphates and indole acetic acid (IAA) production. The resistance to antibiotics was also assessed. Sequencing of the partial 16S rRNA gene was performed and the strains were identified as belonging to different genera. Eight strains, including some identified as Burkholderia fungorum, fixed nitrogen in the free-living state. Eighteen strains exhibited potential to solubilize calcium phosphate, and 13 strains could solubilize aluminum phosphate. High levels of IAA production were recorded with l-tryptophan addition for the strain UFLA04-321 (42.3 μg mL^?1). Strains highly efficient in symbiosis with cowpea bean, including strains already approved as inoculants showed the ability to perform other processes that promote plant growth. Besides, these strains exhibited resistance to several antibiotics. The ability of the nitrogen-fixing bacteria to perform other processes and their adaptation to environmental conditions add value to these strains, which could lead to improved inoculants for plant growth and environmental quality.     

Paenibacillus yonginensis sp. nov., a potential plant growth promoting bacterium isolated from humus soil of Yongin forest

Strain DCY84^T, a Gram-stain positive, rod-shaped, aerobic, spore-forming bacterium, motile by means of peritrichous flagella, was isolated from humus soil from Yongin forest in Gyeonggi province, South Korea. Strain DCY84^T shared the highest sequence similarity with Paenibacillus barengoltzii KACC 15270^T (96.86 %), followed by Paenibacillus timonensis KACC 11491^T (96.49 %) and Paenibacillus phoenicis NBRC 106274^T (95.77 %). Strain DCY84^T was found to able to grow best in TSA at temperature 30 °C, at pH 8 and at 0.5 % NaCl. MK-7 menaquinone was identified as the isoprenoid quinone. The major polar lipids were identified as phosphatidylethanolamine, an unidentified aminophospholipid, two unidentified aminolipids and an unidentified polar lipid. The peptidoglycan was found to contain the amino acids meso-diaminopimelic acid, alanine and d-glutamic acid. The major fatty acids of strain DCY84^T were identified as branched chain anteiso-C_15:0, saturated C_16:0 and branched chain anteiso-C_17:0. The cell wall sugars of strain DCY84^T were found to comprise of ribose, galactose and xylose. The major polyamine was identified as spermidine. The DNA G+C content was determined to be 62.6 mol%. After 6 days of incubation, strain DCY84^T produced 52.96 ± 1.85 and 72.83 ± 2.86 µg/ml l-indole-3-acetic acid, using media without l-tryptophan and supplemented with l-tryptophan, respectively. Strain DCY84^T was also found to be able to solubilize phosphate and produce siderophores. On the basis of the phenotypic characteristics, genotypic analysis and chemotaxonomic characteristics, strain DCY84^T is considered to represent a novel species of the genus Paenibacillus, for which the name Paenibacillus yonginensis sp. nov. is proposed. The type strain is DCY84^T (=KCTC 33428^T = JCM 19885^T).     

Streptomyces leeuwenhoekii sp. nov., the producer of chaxalactins and chaxamycins,forms a distinct branch in Streptomyces gene trees

A polyphasic study was carried out to establish the taxonomic status of an Atacama Desert isolate, Streptomyces strain C34^T, which synthesises novel antibiotics, the chaxalactins and chaxamycins. The organism was shown to have chemotaxonomic, cultural and morphological properties consistent with its classification in the genus Streptomyces. Analysis of 16S rRNA gene sequences showed that strain C34^T formed a distinct phyletic line in the Streptomyces gene tree that was very loosely associated with the type strains of several Streptomyces species. Multilocus sequence analysis based on five house-keeping gene alleles underpinned the separation of strain C34^T from all of its nearest phylogenetic neighbours, apart from Streptomyces chiangmaiensis TA-1^T and Streptomyces hyderabadensis OU-40^T which are not currently in the MLSA database. Strain C34^T was distinguished readily from the S. chiangmaiensis and S. hyderabadensis strains by using a combination of cultural and phenotypic data. Consequently, strain C34^T is considered to represent a new species of the genus Streptomyces for which the name Streptomyces leeuwenhoekii sp. nov. is proposed. The type strain is C34^T (= DSM 42122^T = NRRL B-24963^T). Analysis of the whole-genome sequence of S. leeuwenhoekii, with 6,780 predicted open reading frames and a total genome size of around 7.86 Mb, revealed a high potential for natural product biosynthesis.     

Streptomyces muensis sp. nov.

A strain of Streptomyces, MBRL 179^T, isolated from a sample from a Limestone quarry located at Hundung, Manipur, India, was characterized by polyphasic taxonomy. The strain formed a monophyletic clade with Streptomyces spinoverrucosus NBRC 14228^T (16S rRNA gene sequence similarity of 99.3 %) in the Neighbour-joining tree. DNA–DNA hybridization experiment gave a DNA–DNA relatedness value of 34.7 % between MBRL 179^T and S. spinoverrucosus NBRC 14228^T. Strain MBRL 179^T contained LL-diaminopimelic acid, xylose, glucose, and mannose in the whole cell-wall hydrolysates along with small amount of ribose. The major polar lipids detected were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositolmannoside, with other unknown phospholipids and aminophospholipid. MK-9(H₆), MK-9(H₈) and MK-9(H₄) were the predominant menaquinones detected. The major fatty acids were anteiso-C_16:0 (28.1 %), iso-C_16:0 (20.3 %), C_16:0 (9.4 %) and anteiso-C_17:0 (8.3 %). The G+C content of the genomic DNA was 71.1 %. Based on the polyphasic experiment results, the strain MBRL 179^T merits recognition as a representative of a novel species of the genus Streptomyces for which the name Streptomyces muensis sp. nov. is proposed; the type strain is MBRL 179^T (=JCM 17576^T = KCTC 29124^T).     

Streptomyces amritsarensis sp. nov., exhibiting broad-spectrum antimicrobial activity

A new actinobacterium strain, designated 2A^T, was isolated from a soil sample collected from Guru Nanak Dev University, Punjab (India) and characterized using a polyphasic taxonomic approach. It showed antimicrobial activity against various Gram-positive and Gram-negative bacteria including drug resistant bacteria and fungi. The strain had chemotaxononomic and morphological properties typical of the genus Streptomyces. The 16S rRNA gene sequence of the strain showed 99.9, 99.5 and 99.5 % similarity with Streptomyces flavotricini DSM 40152^T, Streptomyces toxytricini DSM 40178^T and Streptomyces globosus DSM 40815^T, respectively. This strain formed a coherent cluster with them and shared DNA–DNA homology of 37.6 ± 0.6, 34.4 ± 0.5 and 33.1 ± 0.4 % with type strains, S. flavotricini DSM 40152^T, S. globosus DSM 40815^T and S. toxytricini DSM 40178^T, respectively. Further, the strain was readily distinguished from the phylogenetic close relatives in a variety of morphological, physiological and biochemical properties. Based on the genotypic and phenotypic characteristics, it is proposed that strain 2A^T represents a novel species in the genus Streptomyces, for which the name Streptomyces amritsarensis sp. nov. is proposed, with the type strain 2A^T (=MTCC 11845^T=JCM 19660^T).     

Arthrobacter ginsengisoli sp. nov., isolated from soil of a ginseng field

A Gram-staining-positive, catalase-positive, oxidase-negative, non-motile, non-flagellate and rod-shaped bacterium, was designated as DCY81^T, and isolated from soil of a ginseng field in Pocheon province, Republic of Korea. The 16S rRNA gene sequence analysis revealed that strain DCY81^T belonged to the genus Arthrobacter. Major fatty acid was anteiso-C_15:0, while major polar lipids were diphosphatidyglycerol, phatidyglycerol, phosphatidylinositol, monogalactosyldiacylglycerol (GL1), and dimannosyldiacylglycerol (GL2). The dominant quinone was MK-9(H₂). The peptidoglycan type was A3α with an l-Lys–l-Ala–l-Thr–l-Ala interpeptide bridge. The DNA–DNA hybridization relatedness between strain DCY81^T and Arthrobacter siccitolerans LMG 27359^T (98.2 %), Arthrobacter sulfonivorans JCM 13520^T (97.81 %), Arthrobacter scleromae DSM 17756^T (97.59 %), Arthrobacter oxydans KCTC 3383^T (97.3 %) was 39.1 ± 0.2, 62.2 ± 1.6, 36.8 ± 1.1 and 48.3 ± 1.6 %, respectively which show that the genotypic separation of strain DCY81^T from the closest reference strain of the genus Arthrobacter. The DNA G+C content was 65.2 mol%. The genotypic analysis, physiological, and chemotaxonomic results indicate that strain DCY81^T represents a novel species of the genus Arthrobacter. Therefore, Arthrobacter ginsengisoli sp. nov., is proposed as the type strain (=KCTC 29225^T = JCM 19357^T).     

Strategy for pH control and pH feedback-controlled substrate feeding for high-level production of l-tryptophan by Escherichia coli

Optimum production of l-tryptophan by Escherichia coli depends on pH. Here, we established conditions for optimizing the production of l-tryptophan. The optimum pH range was 6.5–7.2, and pH was controlled using a three-stage strategy [pH 6.5 (0–12 h), pH 6.8 (12–24 h), and pH 7.2 (24–38 h)]. Specifically, ammonium hydroxide was used to adjust pH during the initial 24 h, and potassium hydroxide and ammonium hydroxide (1:2, v/v) were used to adjust pH during 24–38 h. Under these conditions, NH₄ ⁺ and K⁺ concentrations were kept below the threshold for inhibiting l-tryptophan production. Optimization was also accomplished using ratios (v/v) of glucose to alkali solutions equal to 4:1 (5–24 h) and 6:1 (24–38 h). The concentration of glucose and the pH were controlled by adjusting the pH automatically. Applying a pH-feedback feeding method, the steady-state concentration of glucose was maintained at approximately 0.2 ± 0.02 g/l, and acetic acid accumulated to a concentration of 1.15 ± 0.03 g/l, and the plasmid stability was 98 ± 0.5 %. The final, optimized concentration of l-tryptophan was 43.65 ± 0.29 g/l from 52.43 ± 0.38 g/l dry cell weight.     

Streptomyces bullii sp. nov., isolated from a hyper-arid Atacama Desert soil

A Streptomyces strain isolated from a hyper-arid Atacama Desert soil was characterised using a polyphasic taxonomic approach. The strain, designated C2^T, had chemical and morphological properties typical of the genus Streptomyces. The isolate formed a branch in the Streptomyces 16S rRNA gene tree together with the type strain of Streptomyces chromofuscus and was also loosely related to Streptomyces fragilis NRRL 2424^T. DNA:DNA relatedness values between the isolate and its two phylogenetic neighbours showed that it formed a distinct genomic species. The strain was readily distinguished from these organisms using a combination of morphological and phenotypic data. Based on the genotypic and phenotypic results, isolate C2^T represents a novel species in the genus Streptomyces, for which the name Streptomyces bullii sp. nov. is proposed. The type strain is C2^T (=CGMCC 4.7019^T = KACC 15426^T).     

Characterization of IAA Production by the Mangrove Cyanobacterium Phormidium sp. MI405019 and Its Influence on Tobacco Seed Germination and Organogenesis

The production of indole-3-acetic acid (IAA) by a mangrove root-associated cyanobacterium, Phormidium sp. MI405019, was demonstrated in this study. The extracellular extract (ECE) of this cyanobacterial culture filtrate was tested on tobacco seed germination and callus differentiation. In ECE treatment, seed germination was increased by 40 % when compared to that of control. In addition, ECE also induced multiple roots from tobacco callus. Further, the factors such as concentration of l-tryptophan and NaCl (salinity) on IAA production were studied. IAA in the medium was initially increased up to a certain period and subsequently decreased in all salinity ranges tested. The amount of IAA production was decreased after 48 h in the culture grown in media amended with 2 % NaCl and without NaCl. However, the IAA concentration was increased up to 96 h in media containing 4 % NaCl. IAA produced by Phormidium sp. MI405019 was extracted from the culture filtrate and its identity was confirmed by thin-layer chromatography and ultra-fast liquid chromatography. To the best of our knowledge, this is the first report of IAA production by cyanobacteria isolated from a mangrove ecosystem. Based on the results in this study, the utilization of Phormidium sp. MI405019 in the aspects of mangrove growth promotion was discussed.     

Recombinant production and characterization of an N-acyl-d-amino acid amidohydrolase from Streptomyces sp. 64E6

N-Acyl-d-amino acid amidohydrolases (d-aminoacylases) are often used as tools for the optical resolution of d-amino acids, which are important products with applications in industries related to medicine and cosmetics. For this study, genes encoding d-aminoacylase were cloned from the genomes of Streptomyces spp. using sequence-based screening. They were expressed by Escherichia coli and Streptomyces lividans. Almost all of the cell-free extracts exhibit hydrolytic activity toward N-acetyl-(Ac-)d-Phe (0.05–6.32 μmol min^?1 mg^?1) under conditions without CoCl₂. Addition of 1 mM CoCl₂ enhanced their activity. Among them, the highest activity was observed from cell-free extracts prepared from S. lividans that possess the d-aminoacylase gene of Streptomyces sp. 64E6 (specific activities were, respectively, 7.34 and 9.31 μmol min^?1 mg^?1 for N-Ac-d-Phe and N-Ac-d-Met hydrolysis). Furthermore, when using glycerol as a carbon source for cultivation, the recombinant enzyme from Streptomyces sp. 64E6 was produced in 4.2-fold greater quantities by S. lividans than when using glucose. d-Aminoacylase from Streptomyces sp. 64E6 showed optimum at pH 8.0–9.0. It was stable at pH 5.5–9.0 up to 30 °C. The enzyme hydrolyzed various N-acetyl-d-amino acids that have hydrophobic side chains. In addition, the activity toward N-chloroacetyl-d-Phe was 2.1-fold higher than that toward N-Ac-d-Phe, indicating that the structure of N-acylated portion of substrate altered the activity.     

Efficient strategy for maintaining and enhancing the huperzine A production of Shiraia sp. Slf14 through inducer elicitation

Huperzine A (HupA), a naturally occurring lycopodium alkaloid, is a potent, highly specific and reversible inhibitor of acetylcholinesterase and is a potential treatment for Alzheimer’s disease. However, isolating HupA from Huperziaceae plants is inefficient; thus, extracting this compound from endophytic fungi may be more controllable and sustainable. However, the large-scale production of this chemical from endophytes is limited by the innate instability of endophytic fungi. In this study, we maintained the stability and viability of the HupA-producing endophytic fungus Shiraia sp. Slf14 and enhanced the HupA titers during fermentation by adding Huperzia serrata extracts (HSE), l-lysine, and acetic acid into the culture as inducers. Adding trace amounts of HupA clearly improved the HupA production of Shiraia sp. Slf14, reaching a maximum content of approximately 40 μg g^?1. Moreover, the addition of HSE and l-lysine promoted HupA production in the flask fermentation. The aforementioned bioprocessing strategy may be potentially applied to other endophytic fungal culture systems for the efficient production of plant secondary metabolites.