Optofluidic characterization of marine algae using a microflow cytometer

The effects of global warming, pollution in river effluents, and changing ocean currents can be studied by characterizing variations in phytoplankton populations. We demonstrate the design and fabrication of a Microflow Cytometer for characterization of phytoplankton. Guided by chevron-shaped grooves on the top and bottom of a microfluidic channel, two symmetric sheath streams wrap around a central sample stream and hydrodynamically focus it in the center of the channel. The lasers are carefully chosen to provide excitation light close to the maximum absorbance wavelengths for the intrinsic fluorophores chlorophyll and phycoerythrin, and the excitation light is coupled to the flow cytometer through the use of an optical fiber. Fluorescence and light scatter are collected using two multimode optical fibers placed at 90-degree angles with respect to the excitation fiber. Light emerging from these collection fibers is directed through optical bandpass filters into photomultiplier tubes. The cytometer measured the optical and side scatter properties of Karenia b., Synechococcus sp., Pseudo-Nitzchia, and Alexandrium. The effect of the sheath-to-sample flow-rate ratio on the light scatter and fluorescence of these marine microorganisms was investigated. Reducing the sample flow rate from 200 μL/min to 10 μL/min produced a more tightly focused sample stream and less heterogeneous signals.     

Purification and characterization of an aspartic protease from the Rhizopus oryzae protease extract,Peptidase R

BackgroundAspartic proteases are a subfamily of endopeptidases that are useful in a variety of applications, especially in the food processing industry. Here we describe a novel aspartic protease that was purified from Peptidase R, a commercial protease preparation derived from Rhizopus oryzae.ResultsAn aspartic protease sourced from Peptidase R was purified to homogeneity by anion exchange chromatography followed by polishing with a hydrophobic interaction chromatography column, resulting in a 3.4-fold increase in specific activity (57.5 × 10³ U/mg) and 58.8% recovery. The estimated molecular weight of the purified enzyme was 39 kDa. The N-terminal sequence of the purified protein exhibited 63–75% identity to rhizopuspepsins from various Rhizopus species. The enzyme exhibited maximal activity at 75°C in glycine–HCl buffer, pH 3.4 with casein as the substrate. The protease was stable at 35°C for 60 min and had an observed half-life of approximately 30 min at 45°C. Enzyme activity was not significantly inhibited by chelation with ethylenediamine tetraacetic acid (EDTA), and the addition of metal ions to EDTA-treated protease did not significantly change enzyme activity, indicating that proteolysis is not metal ion-dependent. The purified enzyme was completely inactivated by the aspartic protease inhibitor Pepstatin A.ConclusionBased on the observed enzyme activity, inhibition profile with Pepstatin A, and sequence similarity to other rhizopuspepsins, we have classified this enzyme as an aspartic protease.     

Antiproliferative activity of biomass extract from Pseudomonas cedrina

BackgroundThe study of plant-associated microorganisms is very important in the discovery and development of bioactive compounds. Pseudomonas is a diverse genus of Gammaproteobacteria comprising more than 60 species capable of establishing themselves in many habitats, which include leaves and stems of many plants. There are reports of metabolites with diverse biological activity obtained from bacteria of this genus, and some of the metabolites have shown cytotoxic activity against cancer cell lines.Because of the high incidence of cancer, research in recent years has focused on obtaining new sources of active compounds that exhibit interesting pharmacodynamic and pharmacokinetic properties that lead to the development of new therapeutic agents.ResultsA bacterial strain was isolated from tumors located in the stem of Pinus patula, and it was identified as Pseudomonas cedrina. Extracts from biomass and broth of P. cedrina were obtained with chloroform:methanol (1:1). Only biomass extracts exhibited antiproliferative activity against human tumor cell lines of cervix (HeLa), lung (A-549), and breast (HBL-100). In addition, a biomass extract from P. cedrina was fractioned by silica gel column chromatography and two diketopiperazines were isolated: cyclo-(l-Prolyl-l-Valine) and cyclo-(l-Leucyl-l-Proline).ConclusionsThis is the first report on the association of P. cedrina with the stems of P. patula in Mexico and the antiproliferative activity of extracts from this species of bacteria against human solid tumor cell lines.How to cite: Sánchez-Tafolla L, Padrón JM, Mendoza G, et al. Antiproliferative activity of biomass extract from Pseudomonas cedrina. Electron J Biotechnol 2019;40. https://doi.org/10.1016/j.ejbt.2019.03.010.     

Production,characterization and kinetic model of biosurfactant produced by lactic acid bacteria

BackgroundBiosurfactants are surface active molecules produced by microorganisms which have the ability to disrupt the plasma membrane. Biosurfactant properties are important in the food, pharmaceutical and oil industries. Lactic acid bacteria can produce cell-bound and excreted biosurfactants.ResultsThe biosurfactant-producing ability of three Lactobacillus strains was analyzed, and the effects of carbon and nitrogen sources and aeration conditions were studied. The three species of lactobacillus evaluated were able to produce biosurfactants in anaerobic conditions, which was measured as the capacity of one extract to reduce the surface tension compared to a control. The decreasing order of biosurfactant production was L. plantarum>Lactobacillus sp.>L. acidophilus. Lactose was a better carbon source than glucose, achieving a 23.8% reduction in surface tension versus 12.9% for glucose. Two complex nitrogen sources are required for growth and biosurfactant production. The maximum production was reached at 48 h under stationary conditions. However, the highest level of production occurred in the exponential phase. Biosurfactant exhibits a critical micelle concentration of 0.359 ± 0.001 g/L and a low toxicity against E. coli. Fourier transform infrared spectroscopy indicated a glycoprotein structure. Additionally, the kinetics of fermentation were modeled using a logistic model for the biomass and the product, achieving a good fit (R² > 0.9).ConclusionsL. plantarum derived biosurfactant production was enhanced using adequate carbon and nitrogen sources, the biosurfactant is complex in structure and because of its low toxicity could be applied to enhance cell permeability in E. coli.How to cite: Montoya Vallejo C, Florez Restrepo MA, Guzmán Duque FL, et al. Production, characterization and kinetic model of biosurfactant produced by lactic acid bacteria. Electron J Biotechnol 2021;53. https://doi.org/10.1016/j.ejbt.2021.06.001     

Antioxidant and anti-dyslipidemic effects of polysaccharidic extract from sea cucumber processing liquor

BackgroundSea cucumber is a seafood of high nutritional value. During its processing, sea cucumber processing liquor is routinely produced, which is usually discarded as waste. The chemical composition of this processing liquor is similar to sea cucumbers themselves. Hence, valuable ingredients, such as functional polysaccharides, could be obtained from them.ResultsBiologically active polysaccharides from sea cucumber processing liquor were extracted through protease hydrolysis and electroosmosis. The analysis revealed that the polysaccharide extract from sea cucumber processing liquor (PESCPL) is predominantly composed of mannose, in addition to some glucose and fucose. The antioxidant activity of PESCPL was analyzed using in vitro. It was demonstrated that PESCPL could effectively scavenge 1,1-diphenyl-2-picrylhydrazyl radicals, hydroxyl radicals, and superoxide anion radicals. The effect of PESCPL was investigated in vivo by using mice model fed with high-fat diets with/without PESCPL supplement. It was shown that PESCPL could increase the catalase and superoxide dismutase activity in the serum and decrease serum malonaldehyde content. Furthermore, mice fed with PESCPL diet showed a considerable decrease in the serum cholesterol and triglyceride levels and an increase in high-density lipoprotein cholesterol levels.ConclusionsOur research highlights that PESCPL is a natural antioxidant and could be utilized as a therapeutic supplement for dyslipidemia.     

Isolation and characterization of mitochondria from goat hearts

Cardiac mitochondria provide energy for the contraction/relaxation cycle. The aim of our study was to isolate and characterize mitochondria from Caprine hearts under control and in-vitro induced ischemia. A decrease in activities of all the enzymes was observed in the ischemic models. Further characterization of proteins was done by SDS-PAGE and BN-PAGE. Lipids have been characterized by analyzing the phospholipids by HPTLC and fatty acids by GLC in both groups. Our results indicated that injury occurs early in the course of ischemia and progresses during ischemia. TBARS and carbonyl content have also been measured. The in-vitro effects of fatty acids have been studied on the enzymes and complexes of mitochondria.     

Purification and characterization of chymotrypsin-like enzyme from rat plasma

A chymotrypsin-like enzyme was purified from rat plasma, involving ammonium sulfate fractionation and chromatographgy on CM-sephadex and red sepharose. The purified enzyme effectively hydrolysed the ester substrates for chymotrypsin (N-acetyl L-tyrosine ethyl ester and N-acetyl L-tryptophan ethyl ester). The Km values for the two substrates were 2.2×10^?3M and 9.0×10^?3M respectively. The hydrolytic activity of the enzyme was inhibited by phenylmethyl sulfonyl fluoride and tosylphenylalanine chloromethylketone, suggesting the presence of serine and histidine at the active centre. The enzyme exhibited anionic nature and possessed a high molecular weight (MW 71,000) as observed by gel exclusion chromatography on Sephadex G-200. The enzyme was stable upon exposure to pH 7.0–9.0, but was inactivated upon heat treatment at 60°C for 5 min.     

虎杖查尔酮合酶PcCHS1基因的克隆与功能分析

从中药虎杖中通过RACE等方法克隆到一个查尔酮合酶基因的全长cDNA,命名为PcCHS1.该cDNA全长1182 bp,编码一个含393个氨基酸的蛋白质.体外酶促活性研究表明,重组PcCHS1在pH 7～8时催化形成查尔酮为其单一产物,在pH 9时除催化形成查尔酮外,还产生一定量的苯亚甲基丙酮.对PcCHS1第216位和第333位氨基酸进行了定点突变研究,结果表明这些位点对PcCHS1的体外酶促活性影响较大.     

黑曲霉Aspergillus nigerS菌株所产β-葡糖苷酶 的纯化和酶学性质

利用黑曲霉Aspergillus niger S菌株, 通过液体发酵的方法, 得到了一种可同时高效水解大豆异黄酮糖苷成大豆异黄酮,水解白藜芦醇苷成白藜芦醇的糖基水解酶.该酶经硫酸铵分级沉淀、离子交换层析及分子排阻色谱纯化得单一条带, 经SDS聚丙烯酰胺凝胶电泳测得该酶的表观分子量约为165ku 1u=1.660540×10-27kg。 ,比通常所报道的传统β-葡糖苷酶都大,该酶的最适反应温度为50℃; 最适pH值为5~10.     

海滩溢油的微生物降解菌株筛选与特性研究

从青岛石化输油管道爆炸污染的海滩中分离出17株石油降解菌,其中4株Z1、Z2、Z3和Z4降解能力较强,经鉴定分别属于假单胞菌、不动杆菌、红平红球菌和茅孢杆菌.研究了菌株的生长特性与其降解石油能力的关系,表明菌株的降解能力与生物量之间呈相关性.数据表明溢油前四天微生物的降解率最高,经过10天的降解,有三株降解率高达76％以上,其中红平红球菌降解率最高达到79.39％.     

区域知识系统的协同研究

信息时代,区域知识系统之间的协同是提高区域竞争力的重要方面.从企业知识与产品关系研究出发.对区域知识系统的协同条件、协同动力与协同影响因素进行了系统研究,认为,企业间知识结构性互补是协同的必要条件.协同效益主要表现为知识规模经济与范围经济,知识编程程度、非贸易依赖和地理临近都会影响协同效率.     

从公共产品视角分析电子政务建设的成本效益

分析了电子政务建设过程中投入产出严重不相符的情况,提出将电子政务评估的工作前移。根据电子政务的公共产品特性,利用支付意愿（WTP）对电子政务的经济效益进行计算。建立不同电子政务方案建设成本效益模型来计算电子政务生命周期中的净现值,挑选净现值较大的建设组合为建设方案,提供一种切实可行的效益评估方法。以达到社会资源效用最大化的目的。     

Identification and characterization of polyubiquitin gene from cDNA library of aspergillus fumigatus

Aspergillus fumigatus (Afu) causes allergic and invasive forms of diseases in humans. In order to identify genes relevant for pathogenesis, a total of 235 cDNA clones were randomly selected and sequenced from cDNA library of Afu. One of the partially sequenced cDNA clones was homologous to polyubiquitin. Sequencing of the complete cDNA clone showed an open reading frame of 912 bases. Comparison with genomic sequence of Afu using BlastN program, revealed that polyubiquitin gene comprises of 992 bases and contains one intron of 80 bases. The recombinant expression of fusion protein showed an approximately molecular weight of 43-kDa on SDS-PAGE. The translation product of the cDNA sequence showed four tandem repeats of 76 amino acid residues in a single polyubiquitin protein and showed 100% identity with polyubiquitin protein sequences of S. cerevisiae, N. crassa, C. albicans, S. pombe, and M. grisae. Polyubiquitin gene is known to play important role in a variety of cellular processes and recently have been implicated in fungal pathogenesis. Identification of polyubiquitin gene of Afu has opened up scope to study its role in understanding Aspergillus biology and pathogenesis.     

1644-1949 年中国粮食生产与运输格局变迁初探

从粮食生产、粮食供需和粮食运输变化等角度,采用对比分析、交互引证等方法,分析1644-1949年(清朝和民国时期)中国粮食生产能力和粮食运输格局的变迁过程,得到以下主要结论:1清代,粮食富余区主要是湘、鄂、赣、皖,粮食不足区主要是闽及粤琼地区。清中后期,川渝和东北地区由粮食自足区变成粮食富余区,同时,苏、浙、京津冀、豫、鲁等成为粮食不足区;民国时期,粮食不足区进一步扩大,而皖、赣、湘、桂和东北地区是主要的粮食富余区;2清代粮食运销以水运为主,陆运为辅,粮食流通主要从经济欠发达地区流向东南沿海经济发达地区。民国时期,川渝不再作为粮食输出省份,皖及东北地区成为主要供应地,鄂成为重要的粮食中转省份。同时粮食运销方式发生显著变化,北方粮食运输形成了铁路和海运相结合的运输网络;南方依然以水运为主,但受到铁路运输和进口粮食的冲击;3经济科技发展、人口增长和变迁、漕运衰落是促使粮食运输格局发生变化的主要因素;4铁路和轮船等新式交通运输工具极大地便利了粮食运输,促进了粮食的商品化,与此同时,新的粮食运输网络带动了沿线城镇经济发展。