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Applied Microbiology and Biotechnology

Christian Eberlein, Thomas Baumgarten, Stephan Starke, Hermann J Heipieper
Bacteria have evolved an array of adaptive mechanisms enabling them to survive and grow in the presence of different environmental stresses. These mechanisms include either modifications of the membrane or changes in the overall energy status, cell morphology, and cell surface properties. Long-term adaptations are dependent on transcriptional regulation, the induction of anabolic pathways, and cell growth. However, to survive sudden environmental changes, bacterial short-term responses are essential to keep the cells alive after the occurrence of an environmental stress factor such as heat shock or the presence of toxic organic solvents...
February 15, 2018: Applied Microbiology and Biotechnology
Tsz Wai Ng, Wing Lam Chan, Ka Man Lai
Finding ways to predict and control the survival of bacterial aerosols can contribute to the development of ways to alleviate a number of crucial microbiological problems. Significant damage in the membrane integrity of Escherichia coli during aerosolization and airborne suspension has been revealed which has prompted the question of how the membrane fatty acid composition and fluidity influence the survival of airborne bacteria. Two approaches of using isogenic mutants and different growth temperatures were selected to manipulate the membrane fatty acid composition of E...
February 15, 2018: Applied Microbiology and Biotechnology
Timo Stressler, Katrin Reichenberger, Claudia Glück, Sebastian Leptihn, Jens Pfannstiel, Paul Swietalski, Andreas Kuhn, Ines Seitl, Lutz Fischer
Kluyveromyces lactis is a common fungal microorganism used for the production of enzyme preparations such as β-galactosidases (native) or chymosin (recombinant). It is generally important that enzyme preparations have no unwanted side activities. In the case of β-galactosidase preparations produced from K. lactis, an unwanted side activity could be the presence of arylsulfatase (EC Due to the action of arylsulfatase, an unpleasant "cowshed-like" off-flavor would occur in the final product...
February 15, 2018: Applied Microbiology and Biotechnology
Sindhu Mathew, Anna Aronsson, Eva Nordberg Karlsson, Patrick Adlercreutz
Xylooligosaccharides (XOS) and arabinoxylooligosaccharides (AXOS) were produced from the insoluble arabinoxylan fraction of pretreated wheat bran by endoxylanases. The glycoside hydrolase (GH) family 10 xylanases GsXyn10A from Geobacillus stearothermophilus and RmXyn10A-CM from Rhodothermus marinus produced the AXOS A 3 X, A 2 XX and A 2 + 3 XX in addition to XOS. RmXyn10A-CM also produced XA 2 + 3 XX due to its non-conserved aglycone region accommodating additional arabinose substitutions in subsite +2. The GH11 enzymes, Pentopan from Thermomyces lanuginosus and NpXyn11A from Neocallimastix patriciarum had minor structural differences affecting hydrogen bonds in subsites -3 and +3, with similar hydrolysis profiles producing XA 3 XX as major AXOS and minor amounts of XA 2 XX but different ratios of X 3 /X 2 ...
February 14, 2018: Applied Microbiology and Biotechnology
Aureliano Agostinho Dias Meirelles, Rosiane Lopes da Cunha, Andreas Karoly Gombert
During downstream operations involved in the purification of hydrophobic biofuels produced by microorganisms, undesired stable emulsions may be formed. Understanding the mechanisms behind this stability is a pre-requisite for designing cost-effective strategies to break these emulsions. In this work, we aimed at increasing our knowledge on the mechanisms responsible for stabilizing yeast-containing oil-in-water emulsions. For this purpose, emulsions containing hexadecane and different yeast-based aqueous phases were prepared and analyzed for phase separation, surface charge density, particle size, and rheology...
February 14, 2018: Applied Microbiology and Biotechnology
Fanny Chaffanel, Florence Charron-Bourgoin, Claire Soligot, Mounira Kebouchi, Stéphane Bertin, Sophie Payot, Yves Le Roux, Nathalie Leblond-Bourget
The adhesion properties of 14 Streptococcus salivarius strains to mucus (HT29-MTX) and non-mucus secreting (Caco-2/TC7) human intestinal epithelial cells were investigated. Ability to adhere to these two eukaryotic cell lines greatly differs between strains. The presence of mucus played a major factor in adhesion, likely due to high adhesiveness to mucins present in the native human mucus layer covering the whole cell surface. Only one S. salivarius strain (F6-1), isolated from the feces of a healthy baby, was found to strongly adhere to HT-29 MTX cells at a level comparable to that of Lactobacillus rhamnosus GG, a probiotic strain considered to be highly adherent...
February 13, 2018: Applied Microbiology and Biotechnology
Barbara Maciejewska, Tomasz Olszak, Zuzanna Drulis-Kawa
Bacteriophages (phages) are viruses that infect bacteria. The "predator-prey" interactions are recognized as a potentially effective way to treat infections. Phages, as well as phage-derived proteins, especially enzymes, are intensively studied to become future alternative or supportive antibacterials used alone or in combination with standard antibiotic regimens treatment. There are many publications presenting phage therapy aspects, and some papers focused separately on the application of phage-derived enzymes...
February 13, 2018: Applied Microbiology and Biotechnology
Yi-Xin Huo, Liwei Guo, Xiaoyan Ma
The carbon and energy needed for bioconversion processes face trade-offs between cell reproduction and chemical synthesis. In most processes, microbial cells containing overexpressed pathway enzymes were accumulated in exponential phase before the productions of value-added chemicals dominate the carbon and energy fluxes in stationary phase. The pathway enzymes need to be continuously supplied to compensate their degradation, but the promoters driving their overexpressions are downregulated under stationary phase or stressed conditions...
February 13, 2018: Applied Microbiology and Biotechnology
Kirubhakaran Puvendran, Kozhiyalam Anupama, Guhan Jayaraman
Hyaluronic acid (HA) is a high-value polysaccharide with many biomedical applications. Microbial production of HA is now replacing the traditional extraction method from rooster combs. Production of medical-grade HA with defined characteristics requires controlled process conditions because there are many fermentation process parameters that affect the microbial synthesis of HA. This necessitates the development of online tools for monitoring multiple analytes during microbial fermentation. Here, we describe the application of in situ transflectance spectroscopy for online quantification of seven major fermentation analytes, viz...
February 13, 2018: Applied Microbiology and Biotechnology
Luiza Cesca Piva, Janice Lisboa De Marco, Lidia Maria Pepe de Moraes, Viviane Castelo Branco Reis, Fernando Araripe Gonçalves Torres
We have investigated the use of the gene coding for acetamidase (amdS) as a recyclable dominant marker for the methylotrophic yeast Komagataella phaffii in order to broaden its genetic toolbox. First, the endogenous constitutive AMD2 gene (a putative acetamidase) was deleted generating strain LA1. A cassette (amdSloxP) was constructed bearing a codon-optimized version of the Aspergillus nidulans amdS gene flanked by loxP sites for marker excision with Cre recombinase. This cassette was successfully tested as a dominant selection marker for transformation of the LA1 strain after selection on plates containing acetamide as a sole nitrogen source...
February 12, 2018: Applied Microbiology and Biotechnology
Libertad Adaya, Modesto Millán, Carlos Peña, Dieter Jendrossek, Guadalupe Espín, Raunel Tinoco-Valencia, Josefina Guzmán, Daniel Pfeiffer, Daniel Segura
A novel poly-3-hydroxybutyrate depolymerase was identified in Azotobacter vinelandii. This enzyme, now designated PhbZ1, is associated to the poly-3-hydroxybutyrate (PHB) granules and when expressed in Escherichia coli, it showed in vitro PHB depolymerizing activity on native or artificial PHB granules, but not on crystalline PHB. Native PHB (nPHB) granules isolated from a PhbZ1 mutant had a diminished endogenous in vitro hydrolysis of the polyester, when compared to the granules of the wild-type strain. This in vitro degradation was also tested in the presence of free coenzyme A...
February 12, 2018: Applied Microbiology and Biotechnology
Cecilia Andreu, Marcel Lí Del Olmo
Yeast display is a powerful strategy that consists in exposing peptides or proteins of interest on the cell surface of this microorganism. Ever since initial experiments with this methodology were carried out, its scope has extended and many applications have been successfully developed in different science and technology fields. Several yeast display systems have been designed, which all involve introducting into yeast cells the gene fusions that contain the coding regions of a signal peptide, an anchor protein, to properly attach the target to the cell surface, and the protein of interest to be exposed, all of which are controlled by a strong promoter...
February 12, 2018: Applied Microbiology and Biotechnology
Yu Zheng, Jun Mou, Jiwei Niu, Shuai Yang, Lin Chen, Menglei Xia, Min Wang
Lactic acid bacteria (LAB) are essential microbiota for the fermentation and flavor formation of Shanxi aged vinegar, a famous Chinese traditional cereal vinegar that is manufactured using open solid-state fermentation (SSF) technology. However, the dynamics of LAB in this SSF process and the underlying mechanism remain poorly understood. Here, the diversity of LAB and the potential driving factors of the entire process were analyzed by combining culture-independent and culture-dependent methods. Canonical correlation analysis indicated that ethanol, acetic acid, and temperature that result from the metabolism of microorganisms serve as potential driving factors for LAB succession...
February 11, 2018: Applied Microbiology and Biotechnology
Yu Zheng, Yangang Chang, Sankuan Xie, Jia Song, Min Wang
Aerobic Acetobacter pasteurianus is one of the most widely used bacterial species for acetic acid and vinegar production. The acetic acid condition is the primary challenge to the industrial application of A. pasteurianus. Thus, numerous endeavors, including strain improvement and process control, have been performed to improve the product formation and acetic acid tolerance of A. pasteurianus. The metabolic features of A. pasteurianus have been gradually elucidated through omic techniques, such as genomics and proteomics...
February 11, 2018: Applied Microbiology and Biotechnology
Lauren C Franco, Sadie Steinbeisser, Grant M Zane, Judy D Wall, Matthew W Fields
Desulfovibrio spp. are capable of heavy metal reduction and are well-studied systems for understanding metal fate and transport in anaerobic environments. Desulfovibrio vulgaris Hildenborough was grown under environmentally relevant conditions (i.e., temperature, nutrient limitation) to elucidate the impacts on Cr(VI) reduction on cellular physiology. Growth at 20 °C was slower than 30 °C and the presence of 50 μM Cr(VI) caused extended lag times for all conditions, but once growth resumed the growth rate was similar to that without Cr(VI)...
February 10, 2018: Applied Microbiology and Biotechnology
Seyed Mohammad Bagher Hashemi, Amin Mousavi Khaneghah, Jorge A Saraiva, Anet Režek Jambrak, Francisco J Barba, Maria J Mota
Date syrup is rich in fermentable sugars and may be used as a substrate for different microbial fermentations, including lactic acid fermentation processes. The beneficial effects of ultrasounds (US) on bioprocesses have been reported for several microorganisms, due to the enhancement of cell growth, as well as improvements in yields and productivities. Therefore, US treatments (30 kHz, 100 W, 10-30 min) were applied to two lactobacilli (Lactobacillus helveticus PTCC 1332 and Lactobacillus acidophilus PTCC 1643), during fermentation using date syrup as substrate...
February 9, 2018: Applied Microbiology and Biotechnology
Magdalena Nagler, Sabine Marie Podmirseg, Gareth Wyn Griffith, Heribert Insam, Judith Ascher-Jenull
The ubiquity and relevance of extracellular DNA (exDNA) are well-known and increasingly gaining importance in many fields of application such as medicine and environmental microbiology. Although sources and types of exDNA are manifold, ratios of specific DNA-molecules inside and outside of living cells can give reliable information about the activity of entire systems and of specific microbial groups or species. Here, we introduce a method to discriminate between internal (iDNA), as well as bound and free exDNA, and evaluate various DNA fractions and related ratios (ex:iDNA) regarding their applicability to be used as a fast, convenient, and reliable alternative to more tedious RNA-based activity measurements...
February 8, 2018: Applied Microbiology and Biotechnology
Adrien Vigneron, Ian M Head, Nicolas Tsesmetzis
In offshore production facilities, large amounts of deaerated seawater are continuously injected to maintain pressure in oil reservoirs and equivalent volumes of fluids, composed of an oil/gas, and water mixture are produced. This process, brewing billions of liters of biphasic fluids particularly rich in microorganisms, goes through complex steel pipeline networks that are particularly prone to biofilm formation. Consequently, offshore facilities are frequently victims of severe microbiologically influenced corrosion...
February 8, 2018: Applied Microbiology and Biotechnology
Marianna Dourou, Dimitra Aggeli, Seraphim Papanikolaou, George Aggelis
Oleaginous microorganisms are able to convert numerous agro-industrial and municipal wastes into storage lipids (single cell oil (SCO)) and are therefore considered as potential biofuel producers. While from an environmental and technological point of view the idea to convert waste materials into fuels is very attractive, the production cost of SCO is not currently competitive to that of conventional oils due to the low productivity of oleaginous microorganisms in combination with the high fermentation cost...
February 8, 2018: Applied Microbiology and Biotechnology
Cátia A Sousa, Helena M V M Soares, Eduardo V Soares
The increasing use of nanoparticles (NPs) has spurred concerns about their toxic effects. This work aimed to assess the potential hazards of nickel oxide (NiO) NPs using the yeast Saccharomyces cerevisiae as a cell model. Yeast cells exposed for 6 h to 100 mg/L NiO NPs presented reduced metabolic activity (esterase activity and FUN-1 dye processing) and enhanced accumulation of reactive oxygen species. NiO NPs induced the loss of cell viability in a dose-dependent manner. Study of the dissolution of NiO NPs in aqueous media, together with the toxicological data, suggests that the nickel released by the NPs cannot explain all the toxic effects observed in S...
February 8, 2018: Applied Microbiology and Biotechnology
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