In vitro antimicrobial and antioxidant activities of bioactive compounds (secondary metabolites) extracted from Streptomyces lydicus A2.

In the present study, we report antibacterial and antioxidant activities of bioactive compounds extracts (ethyl acetate extract, methanolic extract, n-hexane extract) of Streptomyces lydicus A2 isolated from air in Sciencetific and Technological Equipments Building, Walailak University, Thailand. The S. lydicus A2 is potential to produce bioactive compounds showed various biological activities. In previous research, its culture broth or extract shows antimicrobial activity. In this study, extract prepared from S. lydicus A2 stored at -80 oC was reevaluated the antimicrobial activity when grew in various medium and incubation time to find out storage effect towards the antimicrobial activity. The extract (fractions) from S. lydicus A2 still inhibit test bacteria even though it decreases 50% than the extract prepared from S. lydicus A2 without -80 oC storage. Antimicrobial activity against Staphylococcus aureus and Bacillus cereus was only exhibited by the methanolic fraction S. lydicus A2. Only, the ethyl acetate extract was found to possess dose dependent DPPH free radical scavenging. The isolate A2 could be a potential candidate for the development of novel therapeutic agents active against pathogens and free radicals. Further studies on genomic characterization of isolate and structure determination of the bioactive compounds are under progress.

Identification of an antifungal metabolite produced by a potential biocontrol Actinomyces strain A01 / Identificação de um metabólito antifúngico produzido pela cepa Actinomyces A01

Actinomyces strain A01 was isolated from soil of a vegetable field in the suburb of Beijing, China. According to the morphological, cultural, physiological and biochemical characteristics, and 16S rDNA sequence analysis, strain A01 was identified as Streptomyces lydicus. In the antimicrobial spectrum test strain A01 presented a stable and strong inhibitory activity against several plant pathogenic fungi such as Fusarium oxysporum, Botrytis cinerea, Monilinia laxa, etc. However, no antibacterial activity was found. In pot experiments in greenhouse, the development of tomato gray mold was markedly suppressed by treatment with the fermentation broth of the strain A01, and the control efficacy was higher than those of Pyrimethanil and Polyoxin. A main antifungal compound (purity 99.503 percent) was obtained from the fermentation broth of strain A01 using column chromatography and HPLC. The chemical structural analysis with UV, IR, MS, and NMR confirmed that the compound produced by the strain A01 is natamycin, a polyene antibiotic produced by S. chattanovgensis, S. natalensis, and S. gilvosporeus, widely used as a natural biological preservative for food according to previous reports. The present study revealed a new producing strain of natamycin and its potential application as a biological control agent for fungal plant diseases.

A cepa Actinomyces A01 foi isolada do solo de um campo agrícola no subúrbio de Beijing, China. De acordo com as características morfológicas, culturais, fisiológicas e bioquímicas, e análise da sequência 16S rDNA , a cepa A01 foi identificada como Streptomyces lydicus. Nos testes de espectro antimicrobiano, a cepa A01 apresentou atividade inibitória intensa e estável contra vários fungos patogênicos para plantas, como Fusarium oxysporum, Botrytis cinerea, Monilia laxa, etc. Entretanto, não foi encontrada atividade antibacteriana. Em experimentos em estufas, o desenvolvimento do fungo cinza do tomate foi fortemente inibido pelo tratamento com o caldo de fermentação da cepa A01, com eficiência superior à do pyremethanil e polyoxin. Por cromatografia em coluna e HPLC, obteve-se um composto fúngico (pureza 99,503 por cento), cuja análise estrutural por UV, IR, MS e NMR revelou ser natamicina, um antibiótico polienico produzido por S. chattanovgensis, S. natalensis e S.gilvosporeus, empregado como conservador biológico natural em alimentos. O presente estudo relata a detecção de uma nova cepa produtora de natamicina e sua aplicação potencial como um agente de controle biológico de doenças fúngicas em plantas.

Novel process for the simultaneous extraction and degumming of banana fibers under solid-state cultivation

Various process parameters for the production of polygalacturonase by Streptomyces lydicus under solid-state fermentation were optimized. The optimum particle size of wheat bran for polygalacturonase production was in the range of 500-1000 µm. Initial moisture content of 70 percent was found to be the optimum for enzyme production. The most suitable inoculum size was 1.25 x 10(5) CFU/mL and the optimum incubation temperature was 30ºC. Addition of carbon sources resulted in 37 percent increase in enzyme yield (425 U/g), whereas no significant enhancement was obtained on nitrogen supplementation. Maximum enzyme yield was recorded at 72 h. When compared to the initial production medium (108.5 U/g), the enzyme yield was 3.9 fold after optimization. Solid-state fermentation was effectively employed to develop a novel process for the simultaneous extraction and degumming of banana fibers. Streptomyces lydicus was allowed to grow on wheat bran medium in which banana leaf sheath pieces were incorporated and the fiber bundles were separated after a two-step fermentative process.

Vários parâmetros de processo de produção de poligalacturonase por Streptomyces lydicus por fermentação em estado sólido foram otimizados. O tamanho ótimo de partícula de farelo de trigo para a produção de poligalacturonase esteve na faixa de 500 a 1000 mm. O teor inicial de umidade de 70 por cento foi o melhor para a produção da enzima. O inóculo inicial mais adequado foi de 1,25 x 10(5) UFC/mL e a temperatura ótima de incubação foi 30ºC. A adição de fontes de carbono resultou em aumento de 37 por cento no rendimento da enzima (425U/g), enquanto que a suplementação com nitrogênio não melhorou o rendimento. O rendimento máximo da enzima foi obtido em 72h. A otimização resultou em um aumento de 3,9 vezes na quantidade de enzima produzida inicialmente (108,5U/g). A fermentação em estado-sólido foi eficiente para o desenvolvimento de um novo processo de extração e simultânea degomagem. Streptomyces lydicus foi cultivado em meio de farelo de trigo acrescentado de fragmentos de folhas de banana, sendo os feixes de fibras separados após um processo de fermentação em dois passos.

Breeding of High Streptolydigin-Producing Strain by Complex Mutagenesis and Resistance Selection / 微生物学通报

A high Streptolydigin-producing strain Streptomyces lydicus AS 4.2501-L8 with genetic stability was obtained from the original strain S. lydicus AS 4.2501-P28 by mutagenesis with UV and acridine orange, followed by resistance selection. Its yield of Streptolydigin was 177.0 ?g/mL, 96.2% higher than the original strain.