Enhanced endoglucanase production by soil inhabiting Streptomyces sp. strain NAA9 using lignocellulosic biomass

The actinomycete strain NAA9 exhibiting cellulase production potential was identified based on 16S rDNA sequencing and was found belonging to Streptomyces group. On studying the effect of different lignocellulosic biomass on cellulase production by Streptomyces sp. NAA9, Parthenium hysterophorus weed biomass induced highest levels of enzyme production. The enzyme production was further enhanced by optimization of various parameters, under submerged fermentation conditions. The optimized conditions of 2% (w/v) substrate concentration, 40°C temperature, pH 6.0, an incubation period of 6 days and supplementation of the medium with 0.5% ammonium sulfate, resulted in maximum 0.990±0.012 U/ml endoglucanase production. The findings demonstrate the improved cellulase production by Streptomyces strain NAA9 using P. hysterophorus and indicate the potential of this weed biomass in acting as a low-cost natural substrate for cellulase production. The enzyme produced by actinomycete strain can also be utilized in various applications based on the bioconversion of the cellulosic biomass.     

产甲壳素酶菌株的筛选、鉴定及其酶解产物分析

以甲壳素为唯一碳源,从自然发酵的麻虾酱中筛选到1 株产甲壳素酶的放线菌X1。通过形态学、分子生物学以及生理生化实验鉴定为淀粉酶链霉菌（Streptomyces diastaticus）,命名为S. diastaticus strain CS 1801。在30 ℃条件下培养7 d,该菌株所产甲壳素酶活力为117.4 U/L。利用超高效液相色谱-四极杆-飞行时间串联质谱仪对发酵液中成分进行分析,确定甲壳素在淀粉酶链霉菌CS1801作用下分解成壳二糖、壳三糖、壳四糖、壳五糖和壳六糖。     

产溶菌酶白色链霉菌的筛选及鉴定

从广西各地土壤中取样,利用添加金黄色葡萄球菌的LB培养基初筛,然后用含金黄色葡萄球菌的营养盐平板复筛,所得突变株经摇瓶发酵后测定其用蛋白酶K处理前后的粗酶液活力变化,筛选到一株溶菌酶产生菌RJ-36b.通过菌株形态学和16S rDNA保守序列分析,鉴定其为白色链霉菌.对其发酵条件的初步研究表明,在32℃、200 r/m...     

8株窖泥链霉菌对酸、乙醇的适应性研究

对分离自窖泥的8株放线菌进行鉴定,并考察其对窖泥环境中pH值、乙醇的耐受性.采用ISP2液体培养基在pH值2.0～3.5、乙醇浓度3%vol ～6%vol条件下培养链霉菌菌株,结果显示,分属于链霉菌属的8个种的8株放线菌均不能耐受pH值2.0及6%vol的乙醇浓度,均能耐受pH值3.5及3%vol的乙醇浓度,5株链霉菌在pH值3.0时可以生长,2株链霉菌可耐受5%vol乙醇,说明分离自窖泥的多数链霉菌对窖泥环境的适应能力较好,但不同种链霉菌的适应能力存在差异,窖泥环境在长期生产过程中对链霉菌属菌株具有一定的选择驯化作用.     

Scanning electron microscopy of Streptomyces without use of any chemical fixatives

A new, short, and quick method was developed for preparation of specimen for observing Actinomycetes of genus Streptomyces by scanning electron microscopy. The cultures were directly grown on stubs and coated with a film of gold without using any fixative and dehydrating procedures. Using this simple preparation procedure, surface of intact sporing structures of Streptomyces was observed over a range of magnifications. As the preparation procedure is so simple and rapid, this procedure could be most useful for the routine examination and identification of Streptomyces.     

srrG在Streptomyces rochei生物合成抗生素中的功能解析

为探析调节基因srrG对合成抗生素的直接影响以及在γ-丁酸内酯调节系统中的作用,通过构建破坏株、构建相应的重组质粒pRSET-B-srrG并在Escherichia coli BL21-Gold（DE3）pLysS中高效表达、与其他调节基因的破坏株联合培养,发现srrG破坏株无合成抗生素的能力,且在γ-丁酸内酯调节系统中具有一定作用．srrG在Streptomyces rochei合成抗生素中的功能具有重要的意义．     

Ketonization of Proline Residues in the Peptide Chains of Actinomycins by a 4‐Oxoproline Synthase

X‐type actinomycins (Acms) contain 4‐hydroxyproline (Acm X₀) or 4‐oxoproline (Acm X₂) in their β‐pentapeptide lactone rings, whereas their α ring contains proline. We demonstrate that these Acms are formed through asymmetric condensation of Acm half molecules (Acm halves) containing proline with 4‐hydroxyproline‐ or 4‐oxoproline‐containing Acm halves. In turn, we show—using an artificial Acm half analogue (PPL 1) with proline in its peptide chain—their conversion into the 4‐hydroxyproline‐ and 4‐oxoproline‐containing Acm halves, PPL 0 and PPL 2, in mycelial suspensions of Streptomyces antibioticus. Two responsible genes of the Acm X biosynthetic gene cluster of S. antibioticus, saacmM and saacmN, encoding a cytochrome P450 monooxygenase (Cyp) and a ferredoxin were identified. After coexpression in Escherichia coli, their gene products converted PPL 1 into PPL 0 and PPL 2 in vivo as well as in situ in permeabilized cell of the transformed E. coli strain in conjunction with the host‐encoded ferredoxin reductase in a NADH (NADPH)‐dependent manner. saAcmM has high sequence similarity to the Cyp107Z (Ema) family of Cyps, which can convert avermectin B1 into its keto derivative, 4′′‐oxoavermectin B1. Determination of the structure of saAcmM reveals high similarity to the Ema structure but with significant differences in residues decorating their active sites, which defines saAcmM and its orthologues as a distinct new family of peptidylprolineketonizing Cyp.     

产蓝色素放线菌的初步鉴定和蓝色素性质研究

对一株从土壤中筛选出来的产蓝色素的放线菌进行了初步鉴定, 命名为天蓝色链霉菌－１００（Ｓｔｒｅｐｔｏｍ ｙｃｅｓ ｃｏｅｌｉｃｏｌｏｒ－１００ ）,并对蓝色素的性质进行了研究．结果表明此色素无臭无味,水溶性较强．酸性条件下,溶解度随ｐＨ 降低而减小．ｐＨ＜ ８ 时为红色,ｐＨ≥８ 时为蓝色,颜色随ｐＨ 增大而加深．于１００ ℃短时间处理,比较稳定．在ｐＨ 中性的条件下对光（包括紫外光）较稳定．大多数金属离子如Ｂａ２＋ 、Ｋ＋ 等对此色素无影响,Ｍｇ２＋ 使色素增色．Ｆｅ２＋ 在５×１０－４ ｍ ｏｌ／Ｌ时,使色素变性,但在５×１０－５ ｍ ｏｌ／Ｌ时,对色素没有多大影响．Ｐｂ２＋ 可以络合色素,使之沉淀;加入０．２５％ 盐酸乙醇后,色素再溶解．该蓝色素可作为天然色素或天然ｐＨ 指示剂开发．     

Zinc uptake by Streptomyces rimosus biomass using a packed‐bed column

The ability of Streptomyces rimosus biomass to bind zinc ions in batch mode was shown recently. The aim of this study was to determine the zinc uptake capacity by Streptomyces rimosus biomass in continuous mode. Bacterial biomass was able to bind more Zn(II) after pretreatment with sodium hydroxide (1 mol dm⁻³) than without treatment. The maximum adsorption capacity and the adsorption capacity at the saturation point calculated by means of both the exchange zone model and the Thomas model were practically identical of about 2.9 mg_Zn(II) g⁻¹_biomass. This result was lower than the batch adsorption capacity of Streptomyces rimosus, indicating that the packed‐bed is not the most appropriate process to exploit the bacterial biomass adsorption capacity. The effect of zinc concentration in the range of 10 to 200 mg_Zn(II) dm⁻³ on the biosorption capacity of the packed‐bed was not significant. Biomass regeneration with 0.1 mol dm⁻³ HCl gave a 90% recovery of the adsorbed Zn(II). © 1999 Society of Chemical Industry     

发酵法生产利普司他汀的研究进展

利普司他汀（lipstatin）是一种β-内酯分子,能选择性抑制胰脂肪酶的活性,从而减少小肠脂肪的吸收。分析表明,一个利普司他汀分子与一个脂肪酶分子结合,通过活性部位丝氨酸残基的酰化来抑制胰脂肪酶的催化活性。利普司他汀由毒三链霉菌（Streptomyces toxytricini,简称S. toxytricini）生产的一种天然产物。本文综述了利普司他汀的结构特点,分析了利普司他汀市场应用现状,着重论述了发酵法生产利普司他汀的研究进展;提出生物合成利普司他汀的机制尚不清楚,但酰基辅酶A羧化酶（ACCase）复合物在利普司他汀生物合成中起着关键作用。最后,指出当前存在的问题并对代谢工程在利普司他汀产生菌发酵中的应用进行概述,对今后的研究趋势进行了展望。