Determination of microbial diversity in meju,fermented cooked soya beans,using nested PCR‐denaturing gradient gel electrophoresis

Aims: To identify the microbiota in meju, fermented cooked soya beans, that may directly affect the microbial communities of Korean fermented soya bean foods. Methods and Results: Using conventional bacterial 16S rDNA, bacilli‐specific 16S rDNA or fungi 18S rDNA‐specific primers, PCR products were amplified through a series of PCRs using the DNA extracted from ten meju samples. The amplicons were analysed using denaturing gradient gel electrophoresis (DGGE), which showed that Enterococcus durans was commonly detected in nine of ten meju samples. Bacillus subtilis was shown to be the major strain of bacilli in the samples tested. Based on the DGGE analysis of fungi in meju, we determined that Absidia corymbifera, Aspergillus sp. and Candida rugosa were the main fungi in the tested samples. Conclusions: A variety of bacterial and fungal micro‐organisms were identified in meju samples, in addition to the micro‐organisms already known to be present. Significance and Impact of the Study: This is the first report showing the differences and similarities in the populations of micro‐organisms in meju samples using nested PCR‐DGGE, a culture‐independent method. The results may be applicable to the development of improved meju, in which the indigenous micro‐organisms required for fermentation can be standardized.     

The microbiology of Bandji,palm wine of Borassus akeassii from Burkina Faso: identification and genotypic diversity of yeasts,lactic acid and acetic acid bacteria

Aim

To investigate physicochemical characteristics and especially genotypic diversity of the main culturable micro‐organisms involved in fermentation of sap from Borassus akeassii, a newly identified palm tree from West Africa.

Methods and Results

Physicochemical characterization was performed using conventional methods. Identification of micro‐organisms included phenotyping and sequencing of: 26S rRNA gene for yeasts, 16S rRNA and gyrB genes for lactic acid bacteria (LAB) and acetic acid bacteria (AAB). Interspecies and intraspecies genotypic diversities of the micro‐organisms were screened respectively by amplification of the ITS1‐5.8S rDNA‐ITS2/16S‐23S rDNA ITS regions and repetitive sequence‐based PCR (rep‐PCR). The physicochemical characteristics of samples were: pH: 3·48–4·12, titratable acidity: 1·67–3·50 mg KOH g^?1, acetic acid: 0·16–0·37%, alcohol content: 0·30–2·73%, sugars (degrees Brix): 2·70–8·50. Yeast included mainly Saccharomyces cerevisiae and species of the genera Arthroascus, Issatchenkia, Candida, Trichosporon, Hanseniaspora, Kodamaea, Schizosaccharomyces, Trigonopsis and Galactomyces. Lactobacillus plantarum was the predominant LAB species. Three other species of Lactobacillus were also identified as well as isolates of Leuconostoc mesenteroides, Fructobacillus durionis and Streptococcus mitis. Acetic acid bacteria included nine species of the genus Acetobacter with Acetobacter indonesiensis as predominant species. In addition, isolates of Gluconobacter oxydans and Gluconacetobacter saccharivorans were also identified. Intraspecies diversity was observed for some species of micro‐organisms including four genotypes for Acet. indonesiensis, three for Candida tropicalis and Lactobacillus fermentum and two each for S. cerevisiae, Trichosporon asahii, Candida pararugosa and Acetobacter tropicalis.

Conclusion

fermentation of palm sap from B. akeassii involved multi‐yeast‐LAB‐AAB cultures at genus, species and intraspecies level.

Significance and Impact of the Study

First study describing microbiological and physicochemical characteristics of palm wine from B. akeassii. Genotypic diversity of palm wine LAB and AAB not reported before is demonstrated and this constitutes valuable information for better understanding of the fermentation which can be used to improve the product quality and develop added value by‐products.     

Antimicrobial and antiadhesive properties of a biosurfactant isolated from Lactobacillus paracasei ssp. paracasei A20

Aims: The aim of this study was to determine the antimicrobial and antiadhesive properties of a biosurfactant isolated from Lactobacillus paracasei ssp. paracasei A20 against several micro‐organisms, including Gram‐positive and Gram‐negative bacteria, yeasts and filamentous fungi. Methods and Results: Antimicrobial and antiadhesive activities were determined using the microdilution method in 96‐well culture plates. The biosurfactant showed antimicrobial activity against all the micro‐organisms assayed, and for twelve of the eighteen micro‐organisms (including the pathogenic Candida albicans, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus agalactiae), the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were achieved for biosurfactant concentrations between 25 and 50 mg ml^?1. Furthermore, the biosurfactant showed antiadhesive activity against most of the micro‐organisms evaluated. Conclusions: As far as we know, this is the first compilation of data on antimicrobial and antiadhesive activities of biosurfactants obtained from lactobacilli against such a broad group of micro‐organisms. Although the antiadhesive activity of biosurfactants isolated from lactic acid bacteria has been widely reported, their antimicrobial activity is quite unusual and has been described only in a few strains. Significance and Impact of the Study: The results obtained in this study regarding the antimicrobial and antiadhesive properties of this biosurfactant opens future prospects for its use against micro‐organisms responsible for diseases and infections in the urinary, vaginal and gastrointestinal tracts, as well as in the skin, making it a suitable alternative to conventional antibiotics.     

INTERSTRAIN VARIABILITY IN PHYSIOLOGY AND GENETICS OF HETEROSIGMA AKASHIWO (RAPHIDOPHYCEAE) FROM THE WEST COAST OF NORTH AMERICA1

High levels of intraspecific variability are often associated with HAB species, and this variability is likely an important factor in their competitive success. Heterosigma akashiwo (Hada) Hada ex Y. Hara et M. Chihara is an ichthyotoxic raphidophyte capable of forming dense surface‐water blooms in temperate coastal regions throughout the world. We isolated four strains of H. akashiwo from fish‐killing northern Puget Sound blooms in 2006 and 2007. By assessing numerous aspects of biochemistry, physiology, and toxicity, we were able to describe distinct ecotypes that may be related to isolation location, source population, or bloom timing. Contrasting elements among strains were cell size, maximum growth and photosynthesis rates, tolerance of low salinities, amino acid use, and toxicity to the ciliate grazer Strombidinopsis acuminatum (Fauré‐Fremiet). In addition, the rDNA sequences and chloroplast genome of each isolate were examined, and while all rDNA sequences were identical, the chloroplast genome identified differences among the strains that tracked differences in ecotype. H. akashiwo strain 07A, which was isolated from an unusual spring bloom, had a significantly higher maximum potential photosynthesis rate (28.7 pg C · cell^?1 · h^?1) and consistently exhibited the highest growth rates. Strains 06A and 06B were not genetically distinct from one another and were able to grow on the amino acids glutamine and alanine, while the other two strains could not. Strain 07B, which is genetically distinct from the other three strains, exhibited the only nontoxic effect. Thus, molecular tools may support identification, tracking, and prediction of strains and/or ecotypes using distinctive chloroplast gene signatures.     

Reidentification of facultatively alkaliphilic Bacillus firmus OF4 as Bacillus pseudofirmus OF4

With a view toward verifying the original classification of alkaliphilic Bacillus firmus OF4, physiological and biochemical characteristics were more extensively catalogued than in original studies, and this catalog was supplemented with 16S rDNA sequence homology and more extensive DNA–DNA hybridization analyses. Phylogenetic analysis of this alkaliphile based on the comparison of multiple 16S rDNA sequences from Bacillus species indicated that this strain is most closely related to Bacillus pseudofirmus. Consistently, in the DNA–DNA hybridization analysis of the alkaliphile and Bacillus reference strains, the highest level of DNA–DNA relatedness (96%) was found between the alkaliphile and the B. pseudofirmus type strain (DSM 8715^T). The findings support the conclusion that this alkaliphile strain is more closely related to B. pseudofirmus than to B. firmus, and we propose the future use of the designation B. pseudofirmus OF4. Received: April 20, 1999 / Accepted: August 31, 1999     

A novel PCR-based approach for the detection and classification of potential cellulolytic fungal strains isolated from museum items and surrounding indoor environment

Aims: To develop a novel PCR‐based method able to detect potential cellulolytic filamentous fungi and to classify them exploiting the amplification of the cellobiohydrolase gene (cbh‐I) and its polymorphism. Methods and Results: A mixed approach including the combination of (i) fungal cultivation and isolation, (ii) classification of fungal isolates through the amplification of the cbh gene using a fluorescently labelled primer (f‐CBH‐PCR) and (iii) final fungal identification based on amplification and sequencing of the ITS1‐5.8S rDNA‐ITS2 region of the selected fungal strains was developed. By this approach, it was possible to screen 77 fungal strains belonging to 14 genera and 26 species. Conclusions: The f‐CBH‐PCR permitted the discrimination of fungal species, producing typical f‐CBH profiles. Significance and Impact of the Study: In this study, the cbh gene was used as a preliminary classification tool able to differentiate among themselves the fungal members isolated from indoor museum items and surrounding environment. Such mixed approach consented the fast identification of all isolated fungal strains. The f‐CBH‐PCR method demonstrated its discrimination power, and it can be considered as a new molecular system suitable for the classification of fungal strains isolated from different environments.     

Methylosulfonomonas methylovora gen. nov., sp. nov., and Marinosulfonomonas methylotropha gen. nov., sp. nov.: novel methylotrophs able to grow on methanesulfonic acid

Two novel genera of restricted facultative methylotrophs are described; both Methylosulfonomonas and Marinosulfonomonas are unique in being able to grow on methanesulfonic acid as their sole source of carbon and energy. Five identical strains of Methylosulfonomonas were isolated from diverse soil samples in England and were shown to differ in their morphology, physiology, DNA base composition, molecular genetics, and 16S rDNA sequences from the two marine strains of Marinosulfonomonas, which were isolated from British coastal waters. The marine strains were almost indistinguishable from each other and are considered to be strains of one species. Type species of each genus have been identified and named Methylosulfonomonas methylovora (strain M2) and Marinosulfonomonas methylotropha (strain PSCH4). Phylogenetic analysis using 16S rDNA sequencing places both genera in the α-Proteobacteria. Methylosulfonomonas is a discrete lineage within the α-2 subgroup and is not related closely to any other known bacterial genus. The Marinosulfonomonas strains form a monophyletic cluster in the α-3 subgroup of the Proteobacteria with Roseobacter spp. and some other partially characterized marine bacteria, but they are distinct from these at the genus level. This work shows that the isolation of bacteria with a unique biochemical character, the ability to grow on methanesulfonic acid as energy and carbon substrate, has resulted in the identification of two novel genera of methylotrophs that are unrelated to any other extant methylotroph genera. Received: 19 July 1996 / Accepted: 7 October 1996     

Antimicrobial potential of a lipopeptide biosurfactant derived from a marine Bacillus circulans

Aims: To isolate the biologically active fraction of the lipopeptide biosurfactant produced by a marine Bacillus circulans and study its antimicrobial potentials. Methods and Results: The marine isolate B. circulans was cultivated in glucose mineral salts medium and the crude biosurfactant was isolated by chemical isolation method. The crude biosurfactants were solvent extracted with methanol and the methanol extract was subjected to reverse phase high‐performance liquid chromatography (HPLC). The crude biosurfactants resolved into six major fractions in HPLC. The sixth HPLC fraction eluting at a retention time of 27·3 min showed the maximum surface tension‐reducing property and reduced the surface tension of water from 72 mNm^?1 to 28 mNm^?1. Only this fraction was found to posses bioactivity and showed a pronounced antimicrobial action against a panel of Gram‐positive and Gram‐negative pathogenic and semi‐pathogenic micro‐organisms including a few multidrug‐resistant (MDR) pathogenic clinical isolates. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of this antimicrobial fraction of the biosurfactant were determined for these test organisms. The biosurfactant was found to be active against Gram‐negative bacteria such as Proteus vulgaris and Alcaligens faecalis at a concentration as low as 10 μg ml^?1. The biosurfactant was also active against methicillin‐resistant Staphylococcus aureus (MRSA) and other MDR pathogenic strains. The chemical identity of this bioactive biosurfactant fraction was determined by post chromatographic detection using thin layer chromatography (TLC) and also by Fourier transform infrared (FTIR) spectroscopy. The antimicrobial HPLC fraction resolved as a single spot on TLC and showed positive reaction with ninhydrin, iodine and rhodamine‐B reagents, indicating its lipopeptide nature. IR absorption by this fraction also showed similar and overlapping patterns with that of other lipopeptide biosurfactants such as surfactin and lichenysin, proving this biosurfactant fraction to be a lipopeptide. The biosurfactant did not show any haemolytic activity when tested on blood agar plates, unlike the lipopeptide biosurfactant surfactin produced by Bacillus subtilis. Conclusions: The biosurfactant produced by marine B. circulans had a potent antimicrobial activity against Gram‐positive and Gram‐negative pathogenic and semi‐pathogenic microbial strains including MDR strains. Only one of the HPLC fractions of the crude biosurfactants was responsible for its antimicrobial action. The antimicrobial lipopeptide biosurfactant fraction was also found to be nonhaemolytic in nature. Significance and impact of the study: This work presents a nonhaemolytic lipopeptide biosurfactant produced by a marine micro‐organism possessing a pronounced antimicrobial action against a wide range of bacteria. There is a high demand for new antimicrobial agents because of the increased resistance shown by pathogenic micro‐organisms against the existing antimicrobial drugs. This study provides an insight into the search of new bioactive molecules from marine micro‐organisms.     

Improved ATP supply enhances acid tolerance of Candida glabrata during pyruvic acid production

Aims: A major problem in industrial fermentation of organic acids with micro‐organisms is to ensure a suitable pH in the culture broth. To circumvent this problem, we investigated the effect of citrate, which is a widely used auxiliary energy co‐substrate, on cell growth, organic acid production and pH homeostasis among extracellular environment, cytoplasm and vacuole, in the pyruvic acid production by Candida glabrata CCTCC M202019 under different pH conditions. Methods and Results: Analysis of intracellular ATP regeneration, cytoplasmic and vacuolar pH values under different culture conditions points towards a relief of stress when C. glabrata is exposed to lower pH, if citrate is added. When 50 mmol l^?1 citrate was added to the culture medium, the intracellular ATP concentrations increased by 20·5% (pH 5·5), 20·4% (pH 5·0) and 39·3% (pH 4·5), and higher pH gradients among the culture broth, cell cytoplasm and vacuoles resulted. As a consequence, the cell growth and pyruvic acid production of C. glabrata CCTCC M202019 were significantly improved under pH 5·0 and 4·5. Conclusions: The acid tolerance of yeast can be improved by enhancing the ATP supply, which helps to maintain higher pH gradients in the system. Significance and Impact of the Study: The results presented here expand our understanding of the physiological characteristics in eukaryotic micro‐organisms under low pH conditions and provide a potential route for the further improvement of organic acids production process by process optimization or metabolic engineering.     

Development of a colorimetric colony‐screening assay for detection of defluorination by micro‐organisms

Aims: To develop a colorimetric colony‐screening assay to facilitate the isolation of micro‐organisms capable of defluorination. Methods and Results: A metal‐dye chelate, zirconium‐xylenol orange was used to detect fluoride ions released from a fluorinated substrate through microbial metabolism. Depolymerised zirconium reagent gave the greatest visual contrast for the presence of fluoride compared to more polymerised forms of zirconium reagent. The sensitivity of the assay was greatest when the molar ratio of depolymerised zirconium to xylenol orange was 1 : 2. Using depolymerised zirconium and xylenol orange (150 and 300 nmol l^?1 respectively), the assay could detect a fluoride application spot (5 mmol l^?1) containing 50 nmoles of fluoride ions. Most media constituents were well tolerated by the assay, although phosphate ions needed to be restricted to 0·1 g l^?1 and some proteins digest to between 1 and 5 g l^?1. A microbial enrichment culture growing on solidified medium containing 20 mmol l^?1 fluoroacetate was screened using the assay, and defluorinating bacteria belonging to the genus Burkholderia isolated. Conclusions: A method was developed that is sensitive, rapid and reliable for detecting defluorination by micro‐organisms growing on solidified medium. Significance and Impact of the Study: This method can be used to facilitate the isolation of micro‐organisms capable of defluorination.     

Screening and characterization of butanol‐tolerant micro‐organisms

Aims: Poor butanol tolerance of solventogenic stains directly limits their butanol production during industrial‐scale fermentation process. This study was performed to search for micro‐organisms possessing elevated tolerance to butanol. Methods and Results: Two strains, which displayed higher butanol tolerance compared to commonly used solventogenic Clostridium acetobutylicum, were isolated by evolution and screening strategies. Both strains were identified as lactic acid bacteria (LAB). On this basis, a LAB culture collection was tested for butanol tolerance, and 60% of the strains could grow at a butanol concentration of 2·5% (v/v). In addition, an isolated strain with superior butanol tolerance was transformed using a certain plasmid. Conclusions: The results indicate that many strains of LAB possessed inherent tolerance of butanol. Significance and Impact of the Study: This study suggests that LAB strains may be capable of producing butanol to elevated levels following suitable genetic manipulation.     

Wine phenolic compounds influence the production of volatile phenols by wine-related lactic acid bacteria

Aims: To evaluate the effect of wine phenolic compounds on the production of volatile phenols (4‐vinylphenol [4VP] and 4‐ethylphenol [4EP]) from the metabolism of p‐coumaric acid by lactic acid bacteria (LAB). Methods and Results: Lactobacillus plantarum, Lactobacillus collinoides and Pediococcus pentosaceus were grown in MRS medium supplemented with p‐coumaric acid, in the presence of different phenolic compounds: nonflavonoids (hydroxycinnamic and benzoic acids) and flavonoids (flavonols and flavanols). The inducibility of the enzymes involved in the p‐coumaric acid metabolism was studied in resting cells. The hydroxycinnamic acids tested stimulated the capacity of LAB to synthesize volatile phenols. Growth in the presence of hydroxycinnamic acids, especially caffeic acid, induced the production of 4VP by resting cells. The hydroxybenzoic acids did not significantly affect the behaviour of the studied strains. Some of the flavonoids showed an effect on the production of volatile phenols, although strongly dependent on the bacterial species. Relatively high concentrations (1 g l^?1) of tannins inhibited the synthesis of 4VP by Lact. plantarum. Conclusions: Hydroxycinnamic acids were the main compounds stimulating the production of volatile phenols by LAB. The results suggest that caffeic and ferulic acids induce the synthesis of the cinnamate decarboxylase involved in the metabolism of p‐coumaric acid. On the other hand, tannins exert an inhibitory effect. Significance and Impact of the Study: This study highlights the capacity of LAB to produce volatile phenols and that this activity is markedly influenced by the phenolic composition of the medium.     

Butanol production from corncob residue using Clostridium beijerinckii NCIMB 8052

Aims: Not all lactic acid bacteria possess the ability to confer health benefits for the host. Thus, it becomes necessary to screen and characterize numerous strains to obtain ideal probiotics. Here, two Lactobacillus plantarum strains (CECT 7315 and CECT 7316) were isolated and characterized. Methods and Results: In vitro and in vivo tests were carried out for demonstrating the abilities as probiotics of CECT 7315/CECT 7316 Lact. plantarum strains. Both strains showed high ability to survive at gastro‐intestinal tract conditions and to adhere to intestinal epithelial cells, as well as great inhibitory activity against a wide range of enteropathogens and ability to induce the production of anti‐inflammatory cytokine IL‐10. Conclusions: Lactobacillus plantarum CECT 7315/CECT 7316 because of their potential probiotic properties could be excellent candidates for being tested in clinical trials aimed to demonstrate beneficial effects on human health. Significance and Impact of the Study: Probiotics are live micro‐organisms that confer a health benefit for the host. However, not all the lactic acid bacteria possess the ability to confer health benefits for the host. In this study, two Lact. plantarum strains (CECT 7315 and CECT 7316) were isolated and characterized to demonstrate their excellent qualities as potential probiotic strains.     

Phylogenetic diversity of gene sequences isolated from the rumen as analysed using a self‐organizing map (SOM)

Aims: To determine the origins of DNA sequences isolated from the rumen microbial ecosystem using a self‐organizing map (SOM). Methods and Results: DNA sequences other than 16S small subunit ribosomal RNA (SSU rRNA) gene sequences that were detected from the rumen were analysed by the SOM method reported by Abe et al. [2000, Self‐Organizing Map (SOM) unveils and visualizes hidden sequence characteristics of a wide range of eukaryote genomes. Gene 365, 27–34]. Because query sequences positioned by SOM were scattered on the master drawing of SOM, it was suggested that many DNA sequences isolated from the rumen were collected from a broad range of micro‐organisms. Although the results obtained by SOM were similar to those obtained by the neighbour‐joining (NJ) method, SOM was able to presume the phylotypes of the query sequences without information about the 16S SSU rRNA gene sequences and homology searches, and to reveal existence of novel micro‐organisms deduced to be cellulolytic bacteria, archaea and methanotrophic bacterium. Conclusions: As the SOM method defined phylotypes of unreported rumen micro‐organisms, it is presumed that these phylotypes would be involved in rumen fermentation in cooperation with known rumen micro‐organisms. Moreover, it is demonstrated that SOM is a useful tool for affiliating DNA sequences, which have no matches in databases. Significance and Impact of Study: Through SOM analysis, a better means of identifying rumen micro‐organisms and estimating their roles in rumen function was provided.     

Colonisation of soft lining materials by micro‐organisms

doi:10.1111/j.1741‐2358.2009.00300.x
Colonisation of soft lining materials by micro‐organisms Objective: This study evaluated the in vitro adherence of pathogenic micro‐organisms, Candida albicans, Staphylococcus aureus and Pseudomonas aeruginosa, to soft lining materials and their inhibitory effect on these micro‐organisms. Materials and Methods: To measure adherence, specimens of Molloplast B and Ufi Gel P were inoculated [10⁷ colony‐forming units per millimetre (cfu/ml)] with TSB media containing the micro‐organisms. To determine the number of micro‐organisms in the 10^?2–10^?5 dilutions, 25 μl of the suspension were transferred to plates of selective media. Colony counts of each specimen were quantified (cfu/ml). The surface roughness was measured with a perfilometer to assess the relationship between the adherence of micro‐organisms and surface roughness of each material. For the inhibition test, specimens of materials were placed in agar plates inoculated individually with the micro‐organisms. After 48 h, the inhibition zones around the specimens were measured. Results: None of the materials exhibited inhibition zones. The number of cfu/ml of S. aureus and P. aeruginosa were significantly greater than C. albicans for both materials. The Ufi Gel P exhibited greater adherence of C. albicans than Molloplast B. No correlation was observed between the adherence of micro‐organisms and surface roughness. Conclusion: The surface roughness of the materials is not the only factor governing micro‐organism adherence.     

Characterization of novel diesel-degrading strains <Emphasis Type="Italic">Acinetobacter haemolyticus</Emphasis> MJ01 and <Emphasis Type="Italic">Acinetobacter johnsonii</Emphasis> MJ4 isolated from oil-contaminated soil

The diesel-degrading strains, designated as MJ01 and MJ4, were isolated from oil-contaminated soil in Daejeon (South Korea) and were taxonomically characterized using a polyphasic approach and their diesel oil degradation abilities were analyzed. The isolates MJ01 and MJ4 were identified as Acinetobacter haemolyticus and Acinetobacter johnsonii, respectively, based on their 16S rDNA gene sequences, DNA–DNA relatedness, fatty acid profiles and various physiological characteristics. Strains MJ01 and MJ4 were able to use diesel oil as the sole carbon and energy source. Both strains could degrade over 90% of diesel oil with an initial concentration of 20,000 mg/l after incubation for 7 days, the most significant degradation occurred during the first 3 days. To our knowledge, this is the first report on diesel oil-degrading microorganisms among bacterial strains belonging to A. haemolyticus and A. johnsonii.     

Screening and characterization of microorganisms capable of converting iminodiacetonitrile to iminodiacetic acid

For screening and isolation of microorganisms harboring nitrile‐hydrolyzing enzymes that mediate the hydrolysis of iminodiacetonitrile (IDAN) to iminodiacetic acid (IDA), a sensitive and specific high‐throughput screening model was established. This model integrated a solid screen‐selective culture medium plate with bromcresol purple as the pH indicator coupled to Cu‐IDA complex spectrophotometry. Four strains were selected to perform the biotransformation to IDA, which were isolated and identified as Alcaligenes faecalis, Pseudomonas chlororaphis, Pseudomonas putida and Klebsiella pneumoniae, on the basis of 16S rDNA sequence analysis in combination with physiological and biochemical characterization. Moreover, the maximum specific enzyme activity was 73.4 U/g dry cell weight obtained by A. faecalis ZJUTBX11 after optimization of the medium conditions for enzyme production. The results show that the proposed model is a suitable method for screening microorganisms with nitrile‐hydrolyzing enzymes. We suggest the A. faecalis ZJUTBX11 strain to be used for large‐scale bioconversion of IDAN to IDA, because of its excellent performance in the production of IDA.     

Algal swimming velocities signal fatty acid accumulation

The use of microalgae for biofuel production will be beneficial to society if we can produce biofuels at large scales with minimal mechanical energy input in the production process. Understanding micro‐algal physiological responses under variable environmental conditions in bioreactors is essential for the optimization of biofuel production. We demonstrate that measuring micro‐algal swimming speed provides information on culture health and total fatty acid accumulation. Three strains of Chlamydomonas reinhardtii were grown heterotrophically on acetate and subjected to various levels of nitrogen starvation. Other nutrient levels were explored to determine their effect on micro‐algal kinetics. Swimming velocities were measured with two‐dimensional micro‐particle tracking velocimetry. The results show an inverse linear relationship between normalized total fatty acid mass versus swimming speed of micro‐algal cells. Analysis of RNA sequencing data confirms these results by demonstrating that the biological processes of cell motion and the generation of energy precursors are significantly down‐regulated. Experiments demonstrate that changes in nutrient concentration in the surrounding media also affect swimming speed. The findings have the potential for the in situ and indirect assessment of lipid content by measuring micro‐algal swimming kinetics. Biotechnol. Bioeng. 2013; 110: 143–152. © 2012 Wiley Periodicals, Inc.