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Johan Schnurer – One of the best experts on this subject based on the ideXlab platform.

  • Pichia Anomala J121: a 30-year overnight near success biopreservation story
    Antonie van Leeuwenhoek, 2011
    Co-Authors: Johan Schnurer, Anders Jonsson

    Abstract:

    Thirty years ago, the ascomycetous yeast Pichia Anomala strain J121 was isolated from moist wheat grain stored under conditions of restricted air access. Early observations indicated that an inverse relationship existed between mould and P.   Anomala colony forming units in grain. This yeast strain was later found to have strong antifungal properties in laboratory, pilot and farm studies with high-moisture wheat under malfunctioning airtight storage. P. Anomala had the highest inhibitory activity of 60 yeast species evaluated against the mould Penicillium roqueforti . It also demonstrated strong inhibitory effects against certain Gram-negative bacteria. P.   Anomala J121 possesses a number of physiological characteristics, i.e. capacity to grow under low pH, low water activity and low oxygen tension and ability to use a wide range of carbon and nitrogen sources, enabling it to act as an efficient biopreservative agent. The biocontrol effect in grain was enhanced by addition of glucose, mainly through formation of the volatile antimicrobial ethyl acetate. Animal feeding trials with P. Anomala J121 inoculated grains, fed to chickens and beef cattle, demonstrated that mould control observed in vitro in small scale laboratory experiments could be extended to large scale farm trials. In addition, no adverse effects on animal weight gain, feed conversion, health or behaviour were observed. We have now studied P. Anomala J121 biology, ecology and grain preservation ability for 30 years. Over this period, more than 40 scientific publications and five PhD theses have been written on different aspects of this yeast strain, extending from fundamental research on metabolism, genetics and molecular biology, all the way to practical farm-scale level. In spite of the well documented biopreservative ability of the yeast, it has to date been very difficult to create the right constellation of technical, agricultural and biotechnical industries necessary to reach a commercial launch of a P. Anomala J121 based biopreservation system. Additionally, the complications caused by a complex EU regulatory system remain a significant barrier to practical applications.

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  • Past, present and future research directions with Pichia Anomala.
    Antonie van Leeuwenhoek, 2010
    Co-Authors: Volkmar Passoth, Matilda Olstorpe, Johan Schnurer

    Abstract:

    The first International Pichia Anomala Symposium provided a survey of past, recent and ongoing research on this yeast. The research community working with this yeast has focussed on several areas. Based on molecular data, a revision of the taxonomy is required: the name P. Anomala is no longer applicable, as the genus Pichia is polyphyletic. The current debate centres on whether the yeast should be designated as Wickerhamomyces anomalus or if the previous name, Hansenula Anomala, should be re-instated. The anti-microbial activities of this yeast received considerable attention during the symposium. H. Anomala has been extensively studied as a biopreservation agent in many different post-harvest systems. Several mechanisms account for its anti-microbial activities, including the production of killer proteins and toxic volatile metabolites. Anti-idiotypic antibodies generating an “internal image” of a killer protein have been found to possess therapeutic activity against a broad range of microorganisms. A great diversity of H. Anomala strains was reported at the symposium. Strains have been isolated from several food and feed systems and even from the intestine and reproductive organs of a malaria vector (Anopheles stephensi). Feed and food supplemented with certain H. Anomala strains show an improved quality due, for example, to the addition of advantageous proteins and phytase activity. However, a number of apparent opportunistic pathogenic strains have also been isolated. Strain differentiation, especially the recognition of potentially pathogenic isolates, is an important challenge for the future commercialisation of this yeast. Future industrial and agricultural application of this yeast also raises questions of the economics of large-scale production, its survival during storage (formulation) and of safety regulations, all of which require further investigation.

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  • Biotechnology, physiology and genetics of the yeast Pichia Anomala
    Fems Yeast Research, 2006
    Co-Authors: Volkmar Passoth, Elisabeth Fredlund, Ulrika Ädel Druvefors, Johan Schnurer

    Abstract:

    The ascomycetous yeast Pichia Anomala is frequently associated with food and feed products, either as a production organism or as a spoilage yeast. It belongs to the nonSaccharomyces wine yeasts and contributes to the wine aroma by the production of volatile compounds. The ability to grow in preserved food and feed environments is due to its capacity to grow under low pH, high osmotic pressure and low oxygen tension. A new application of P. Anomala is its use as a biocontrol agent, which is based on the potential to inhibit a variety of moulds in different environments. Although classified as a biosafety class-1 organism, cases of P. Anomala infections have been reported in immunocompromised patients. On the other hand, P. Anomala killer toxins have a potential as antimicrobial agents. The yeast can use a broad range of nitrogen and phosphor sources, which makes it a potential agent to decrease environmental pollution by organic residues from agriculture. However, present knowledge of the physiological basis of its performance is limited. Recently, the first studies have been published dealing with the global regulation of the metabolism of P. Anomala under different conditions of oxygenation.

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Arunaloke Chakrabarti – One of the best experts on this subject based on the ideXlab platform.

  • PCR-based identification and strain typing of Pichia Anomala using the ribosomal intergenic spacer region IGS1.
    Journal of medical microbiology, 2007
    Co-Authors: Sonia Bhardwaj, Rajeshwari Sutar, Anand K. Bachhawat, Sunit Singhi, Arunaloke Chakrabarti

    Abstract:

    Frequent outbreaks of Pichia Anomala fungaemia in paediatric patients have warranted the development of a rapid identification system for this organism. This study describes a specific PCR-based method targeting the rRNA gene intergenic spacer region 1 (IGS1) for rapid identification of Pichia Anomala isolates and characterization at the strain level. These methods of species identification and strain typing were used on 106 isolates of Pichia Anomala (77 from a previously described outbreak and 29 isolated post-outbreak from the same hospital). Using conventional morphological and biochemical methods, 11 strains isolated during the outbreak were misidentified as P. Anomala. blast analysis of sequences of internal transcribed spacer (ITS) regions of rRNA genes confirmed that they were Pichia guilliermondii (eight isolates) and Debaryomyces hansenii (three isolates). Strain typing of Pichia Anomala isolates confirmed the previous finding of a point-source outbreak. The results suggest that IGS sequences and their polymorphisms could be exploited for similar typing methods in other organisms.

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  • Comparison of ITS and IGS1 regions for strain typing of clinical and non-clinical isolates of Pichia Anomala.
    Journal of Medical Microbiology, 2004
    Co-Authors: Rajeshwari Sutar, Joseph K David, K. Ganesan, Anup K. Ghosh, Sunit Singhi, Arunaloke Chakrabarti, Anand K. Bachhawat

    Abstract:

    Pichia Anomala is an emerging nosocomial pathogen and there is a need for methods that distinguish between different P. Anomala strains. In the typing of several clinical as well as non-clinical P. Anomala strains, the sequence variation of the internal transcribed spacer (ITS) was found to be inadequate for typing purposes. The intergenic spacer 1 (IGS1) region of the rDNA of several P. Anomala strains was therefore investigated in detail. The IGS1 region (which varied from 1213 to 1231 bp in length) was interspersed with repeats and had more variation than the ITS regions. Comparative analysis in cases where analysis by the ITS was ambiguous clearly revealed the IGS1 region to be a more discriminatory tool in the typing of P. Anomala strains.

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  • outbreak of pichia Anomala infection in the pediatric service of a tertiary care center in northern india
    Journal of Clinical Microbiology, 2001
    Co-Authors: Arunaloke Chakrabarti, K Singh, A Narang, S Singhi, R Batra, K L N Rao, Pallab Ray, S Gopalan, S Das, V Gupta

    Abstract:

    An outbreak of nosocomial fungemia due to the unusual yeast, Pichia Anomala occurred in the pediatric wards of our hospital over a period of 23 months (April 1996 to February 1998). A total of 379 neonates and children (4.2% admissions) were infected. The probable index case was admitted to the pediatric emergency ward, with subsequent transmission to the premature nursery, pediatric intensive care units, and other children wards. Carriage on the hands of health care personnel was likely to be responsible for dissemination of the fungus. The outbreak could only be controlled after a health education campaign to improve hand-washing practices was instituted and after nystatin-fluconazole prophylaxis to all premature neonates and high-risk infants was introduced. In a case-control study, we identified a lower gestational age, a very low birth weight (<1,500 g), and a longer duration of hospital stay as significant risk factors associated with P. Anomala fungemia in premature neonates. We conducted a culture prevalence survey of 50 consecutive premature neonates and found that 28% were colonized with P. Anomala at a skin or mucosal site on the date of delivery and that 20% of these neonates subsequently developed P. Anomala fungemia. We performed multilocus enzyme electrophoresis on 40 P. Anomala outbreak isolates (including patient and health care workers’ hand isolates), and the results suggested that these isolates were identical. Our study highlights the importance of P. Anomala as an emerging nosocomial fungal pathogen.

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Elisabeth Fredlund – One of the best experts on this subject based on the ideXlab platform.

  • Biotechnology, physiology and genetics of the yeast Pichia Anomala
    Fems Yeast Research, 2006
    Co-Authors: Volkmar Passoth, Elisabeth Fredlund, Ulrika Ädel Druvefors, Johan Schnurer

    Abstract:

    The ascomycetous yeast Pichia Anomala is frequently associated with food and feed products, either as a production organism or as a spoilage yeast. It belongs to the nonSaccharomyces wine yeasts and contributes to the wine aroma by the production of volatile compounds. The ability to grow in preserved food and feed environments is due to its capacity to grow under low pH, high osmotic pressure and low oxygen tension. A new application of P. Anomala is its use as a biocontrol agent, which is based on the potential to inhibit a variety of moulds in different environments. Although classified as a biosafety class-1 organism, cases of P. Anomala infections have been reported in immunocompromised patients. On the other hand, P. Anomala killer toxins have a potential as antimicrobial agents. The yeast can use a broad range of nitrogen and phosphor sources, which makes it a potential agent to decrease environmental pollution by organic residues from agriculture. However, present knowledge of the physiological basis of its performance is limited. Recently, the first studies have been published dealing with the global regulation of the metabolism of P. Anomala under different conditions of oxygenation.

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  • Central Carbon Metabolism in the Biocontrol Yeast Pichia Anomala Influence of Oxygen Limitation
    , 2004
    Co-Authors: Elisabeth Fredlund

    Abstract:

    Fredlund, E. 2004. Central Carbon Metabolism of the Biocontrol Yeast Pichia Anomala Influence of Oxygen Limitation. Doctor’s dissertation. ISSN 1401-6249, ISBN 91-576-6767-5. The biocontrol yeast Pichia Anomala prevents mould damage of moist cereal grain during malfunctioning airtight storage but it can also spoil food and feed. This thesis focuses on the physiology and metabolism of P. Anomala, in particular during oxygen limitation, a condition relevant to airtight storage of cereal grain. P. Anomala grew under strictly anaerobic conditions, at temperatures between 3oC and 37oC, pH values between 2.0 and 12.4, low water activity (0.85), and on many different nutrients. Accumulation of low-molecular compounds in living cells was analysed by HR MAS-NMR. Glycerol, arabitol, and trehalose accumulation increased with reduced oxygen availability, indicating a role during oxygen-limited growth. Regulation of the central aerobic and hypoxic metabolism of P. Anomala was investigated under controlled fermentor conditions. Oxygen limitation induced alcoholic fermentation as well as activity of the key fermentative enzymes, ADH and PDC. Metabolic flux analysis revealed that the TCA pathway operated as a cycle during aerobic batch culture and as a twobranched pathway under oxygen limitation. Hypoxic conditions also increased the production of ethyl acetate, an ester involved in the biocontrol activity of P. Anomala. Genes encoding the ADH and PDC enzymes were cloned, PaADH1, PaADH2, and PaPDC1, and their expression was analysed with real-time RT-PCR. PaADH1 and PaPDC1 were expressed during aerobic growth on glucose and ethanol and were up-regulated in response to oxygen limitation. PaADH2 expression was low during these growth conditions, i.e.

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  • Physiological characteristics of the biocontrol yeast Pichia Anomala J121
    FEMS yeast research, 2002
    Co-Authors: Elisabeth Fredlund, Ulrika Ädel Druvefors, Marianne E. Boysen, Karl-johan Lingsten, Johan Schnurer

    Abstract:

    The yeast Pichia Anomala J121 prevents mold spoilage and enhances preservation of moist grain in malfunctioning storage systems. Development of P. Anomala J121 as a biocontrol agent requires in-depth knowledge about its physiology. P. Anomala J121 grew under strictly anaerobic conditions, at temperatures between 3°C and 37°C, at pH values between 2.0 and 12.4, and at a water activity of 0.92 (NaCl) and 0.85 (glycerol). It could assimilate a wide range of C- and N-sources and produce killer toxin. A selective medium containing starch, nitrate, acetic acid, and chloramphenicol was developed for P. Anomala. P. Anomala was equally sensitive as Candida albicans to common antifungal compounds. Growth ability at a range of environmental conditions contributes to the competitive ability of the biocontrol yeast P. Anomala J121.

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