The Experts below are selected from a list of 90 Experts worldwide ranked by ideXlab platform
Robert A. Samson - One of the best experts on this subject based on the ideXlab platform.
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Sexual reproduction as the cause of heat resistance in the food spoilage fungus Byssochlamys spectabilis (anamorph Paecilomyces variotii).
Applied and environmental microbiology, 2008Co-Authors: Jos Houbraken, János Varga, Emilia Rico-munoz, Shawn Johnson, Robert A. SamsonAbstract:Paecilomyces variotii is a common cosmopolitan species that is able to spoil various food- and feedstuffs and is frequently encountered in heat-treated products. However, isolates from heat-treated products rarely form ascospores. In this study we examined by using molecular techniques and mating tests whether this species can undergo a sexual cycle and form ascospores. The population structure of this species was examined by analyzing the nuclear ribosomal internal transcribed spacer 1 (ITS1) and ITS2 and the 5.8S rRNA gene, as well as partial β-tubulin, actin, and calmodulin gene sequences. Phylogenetic analyses revealed that P. variotii is a highly variable species. Partition homogeneity tests revealed that P. variotii has a recombining population structure. In addition to sequence analyses, mating experiments indicated that P. variotii is able to form ascomata and ascospores in culture in a heterothallic manner. The distribution of MAT1-1 and MAT1-2 genes showed a 1:1 ratio in the progeny of the mating experiments. From the sequence analyses and mating data we conclude that P. variotii is the anamorph of Talaromyces spectabilis and that it has a biallelic heterothallic mating system. Since Paecilomyces sensu stricto anamorphs group within Byssochlamys, a new combination Byssochlamys spectabilis is proposed.
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Activation of ascospores by novel food preservation techniques
Advances in experimental medicine and biology, 2006Co-Authors: Jan Dijksterhuis, Robert A. SamsonAbstract:Most fungal survival structures can be regarded as heat resistant to some extent: sclerotia, conidia and ascospores can survive temperatures between 55 and 95°C. Byssochlamys, Neosartorya and Talaromyces are the most well known heat-resistant fungal genera. Ascospores of these fungi are the most resilient eukaryotic structures currently known. A decimal reduction time of 1.5-11 min at 90°C has been reported for some species (Scholte et al., 2004). Recently, Panagou et al. (2002) reported moderate heat resistance (D75 4.9-7.8 min) in ascospores of Monascus ruber isolated from brine of a commercial thermally processed can of green olives. There appeared to be a complex interaction between pH and salt content of the heating menstruum and decimal reduction time for this fungus. During recent work undertaken in our laboratory, moderate heat resistance has been observed for Talaromyces stipitatus and T. helicus (J. Dijksterhuis, unpublished results), and studies involving ascospores of Byssochlamys spectabilis have resulted in a calculated decimal reduction time at 85°C of 47-75 min (J. Houbraken, unpublished results). Table 1 shows a compilation of heat resistance data for many known heat resistant species and their D values in various heating menstrua (modified from Scholte et al., 2004).
Huoqing Huang - One of the best experts on this subject based on the ideXlab platform.
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A novel thermostable aspartic protease from Talaromyces leycettanus and its specific autocatalytic activation through an intermediate transition state.
Applied microbiology and biotechnology, 2020Co-Authors: Guo Yujie, Tu Tao, Jie Zheng, Yaxin Ren, Yaru Wang, Yingguo Bai, Su Xiaoyun, Wang Yuan, Bin Yao, Huoqing HuangAbstract:Aspartic proteases exhibit optimum enzyme activity under acidic conditions and have been extensively used in food, fermentation, and leather industries. In this study, a novel aspartic protease precursor (proTlAPA1) from Talaromyces leycettanus was identified and successfully expressed in Pichia pastoris. Subsequently, the auto-activation processing of the zymogen proTlAPA1 was studied by SDS-PAGE and N-terminal sequencing, under different processing conditions. TlAPA1 shared the highest identity of 70.3% with the aspartic endopeptidase from Byssochlamys spectabilis (GAD91729) and was classified into a new subgroup of the aspartic protease A1 family, based on evolutionary analysis. Mature TlAPA1 protein displayed an optimal activity at 60 °C and remained stable at temperatures of 55 °C and below, indicating the thermostable nature of TlAPA1 aspartic protease. During the auto-activation processing of proTlAPA1, a 45-kDa intermediate was identified that divided the processing mechanism into two steps: formation of intermediates and activation of the mature protein (TlAPA1). The former step can be processed without proteolytic activity, while the latter process depended on protease activity completely. The discovery of the novel aspartic protease TlAPA1 and the study of its activation process will contribute to a better understanding of the mechanism of aspartic protease auto-activation.
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A novel thermostable aspartic protease from Talaromyces leycettanus and its specific autocatalytic activation through an intermediate transition state
2019Co-Authors: Guo Yujie, Tu Tao, Yaxin Ren, Yaru Wang, Yingguo Bai, Su Xiaoyun, Wang Yuan, Bin Yao, Huoqing Huang, Huiying LuoAbstract:ABSTRACT Aspartic proteases exhibit optimum enzyme activity under acidic condition and have been extensively used in food, fermentation and leather industries. In this study, a novel aspartic protease precursor (proTlAPA1) from Talaromyces leycettanus was identified and successfully expressed in Pichia pastoris. Subsequently, the auto-activation processing of the zymogen proTlAPA1 was studied by SDS-PAGE and N-terminal sequencing, under different processing conditions. TlAPA1 shared the highest identity of 70.3 % with the aspartic endopeptidase from Byssochlamys spectabilis (GAD91729) and was classified into a new subgroup of the aspartic protease A1 family, based on evolutionary analysis. Mature TlAPA1 protein displayed an optimal activity at 60 °C and remained stable at temperatures of 55 °C and below, indicating the thermostable nature of TlAPA1 aspartic protease. During the auto-activation processing of proTlAPA1, a 45 kDa intermediate was identified that divided the processing mechanism into two steps: formation of intermediates, and activation of the mature protein (TlAPA1). The former step was completely induced by pH of the buffer, while the latter process depended on protease activity. The discovery of the novel aspartic protease TlAPA1 and study of its activation process will contribute to a better understanding of the mechanism of aspartic proteases auto-activation. IMPORTANCE The novel aspartic protease TlAPA1 was identified from T. leycettanus and expressed as a zymogen (proTlAPA1) in P. pastoris. Enzymatic characteristics of the mature protein were studied and the specific pattern of zymogen conversion was described. The auto-activation processing of proTlAPA1 proceeded in two stages and an intermediate was identified in this process. These results describe a new subgroup of aspartic protease A1 family and provide insights into a novel mode of activation processing in aspartic proteases.
Olga I. Padilla-zakour - One of the best experts on this subject based on the ideXlab platform.
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High pressure processing of spoilage fungi as affected by water activity in a diluted apple juice concentrate
Food Control, 2020Co-Authors: Elizabeth C. Buerman, Randy W. Worobo, Olga I. Padilla-zakourAbstract:Abstract High Pressure Processing (HPP) is a method used to extend shelf life of foods by subjecting products in their final packaging to extreme pressure. This leads to protein degradation in microbial cells, membrane degradation, and eventual cell death. Survival of spoilage organisms, especially spore-formers, has not been closely considered in regard to the effect of water activity (aw). The purpose of this study was to determine the effect of pH and aw on HPP apple juice to prevent fungal spoilage during shelf life. Apple juice concentrate was adjusted to aw 0.94 (39.3°Brix), 0.96 (32.2°Brix), 0.98 (22.0°Brix), or 1.00 (7.1°Brix) and pH 4.6 or pH 7.0. Polyethylene terephthalate bottles were filled with concentrate and inoculated with Penicillium spp., Aspergillus niger, Byssochlamys spectabilis, Rhodotorula mucilaginosa, Candida parapsilosis, Torulaspora delbrueckii, or Brettanomyces bruxellensis. Samples were HPP treated at 450 MPa for 1.5 min and for pressure-resistant species, at 600 MPa for 1.5 min or 3 min to resemble industrial processing conditions. Fungi were more resistant to HPP at lower aw and higher pH. C. parapsilosis was more resistant to HPP than the other organisms tested. Fungi, with the exception of C. parapsilosis, experienced a 4.26- or greater log reduction at aw of 0.98 and above at either pH. Their reductions ranged from 0.5 to 5.3 log reduction at 0.94 aw and 0.96 aw with pH 4.6. The reductions were 0.1–4.5-log at 0.94 and 0.96 aw at pH 7.0. In general, shelf life was a matter of weeks at ambient temperatures and 7.0 pH, even when processing pressures were increased to 600 MPa. To reduce risk of fungal spoilage, HPP products should be at or above 0.98 aw and below 4.6 pH and stored at refrigerated conditions.
Yoshiyuki Nomura - One of the best experts on this subject based on the ideXlab platform.
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(NBRC109023)
2016Co-Authors: Takuji Oka, Keisuke Ekino, Kohsai Fukuda, Yoshiyuki NomuraAbstract:Byssochlamys spectabilis no. 5 (anamorph Paecilomyces variotii no. 5) (NBRC109023) was isolated from a soil sample in 2001 in Kumamoto Prefecture, Japan. This fungus is highly resistant to formaldehyde. Here, we report a draft genome sequence of P. variotii no. 5; this draft was produced with the intent of investigating the mechanism of formaldehyde resistance. This is the first report of the genome sequence of any Paecilomyces species
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Isolation, sequencing, and heterologous expression of the Paecilomyces variotii gene encoding S-hydroxymethylglutathione dehydrogenase (fldA)
Applied Microbiology and Biotechnology, 2015Co-Authors: Takuji Oka, Keisuke Ekino, Kohsai Fukuda, Yuji Komachi, Kazufumi Ohshima, Yoichi Kawano, Kazuhiro Nagahama, Yoshiyuki NomuraAbstract:The filamentous fungus Paecilomyces variotii NBRC 109023 (teleomorph: Byssochlamys spectabilis NBRC 109023) degrades formaldehyde at concentrations as high as 2.4 % ( w / v ). In many prokaryotes and in all known eukaryotes, formaldehyde degradation is catalyzed by S -hydroxymethylglutathione ( S -HMGSH) dehydrogenase. We report here the isolation and characterization of the gene encoding S -HMGSH dehydrogenase activity in P. variotii . The 1.6-kb fldA gene contained 5 introns and 6 exons, and the corresponding cDNA was 1143 bp, encoding a 40-kDa protein composed of 380 amino acids. FldA was predicted to have 74.3, 73.7, 68.5, and 67.4 % amino acid identity to the S -HMGSH dehydrogenases of Hansenula polymorpha , Candida boidinii , Saccharomyces cerevisiae , and Kluyveromyces lactis , respectively. The predicted protein also showed high amino acid similarity (84∼86 %) to the products of putative fldA genes from other filamentous fungi, including Aspergillus sp. and Penicillium sp. Notably, the P. variotii fldA gene was able to functionally complement a Saccharomyces cerevisiae strain (BY4741 ∆ sfa1 ) lacking the gene for S -HMGSH dehydrogenase. The heterologous expression construct rendered BY4741 ∆ sfa1 tolerant to exogenous formaldehyde. Although BY4741 (parental wild-type strain) was unable to degrade even low concentrations of formaldehyde, BY4741 ∆ sfa1 harboring Paecilomyces fldA was able to degrade 4 mM formaldehyde within 30 h. The findings from this study confirm the essential role of S -HMGSH dehydrogenase in detoxifying formaldehyde.
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Draft Genome Sequence of the Formaldehyde-Resistant Fungus Byssochlamys spectabilis No. 5 (Anamorph Paecilomyces variotii No. 5) (NBRC109023).
Genome announcements, 2014Co-Authors: Takuji Oka, Keisuke Ekino, Kohsai Fukuda, Yoshiyuki NomuraAbstract:Byssochlamys spectabilis no. 5 (anamorph Paecilomyces variotii no. 5) (NBRC109023) was isolated from a soil sample in 2001 in Kumamoto Prefecture, Japan. This fungus is highly resistant to formaldehyde. Here, we report a draft genome sequence of P. variotii no. 5; this draft was produced with the intent of investigating the mechanism of formaldehyde resistance. This is the first report of the genome sequence of any Paecilomyces species.
Guo Yujie - One of the best experts on this subject based on the ideXlab platform.
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A novel thermostable aspartic protease from Talaromyces leycettanus and its specific autocatalytic activation through an intermediate transition state.
Applied microbiology and biotechnology, 2020Co-Authors: Guo Yujie, Tu Tao, Jie Zheng, Yaxin Ren, Yaru Wang, Yingguo Bai, Su Xiaoyun, Wang Yuan, Bin Yao, Huoqing HuangAbstract:Aspartic proteases exhibit optimum enzyme activity under acidic conditions and have been extensively used in food, fermentation, and leather industries. In this study, a novel aspartic protease precursor (proTlAPA1) from Talaromyces leycettanus was identified and successfully expressed in Pichia pastoris. Subsequently, the auto-activation processing of the zymogen proTlAPA1 was studied by SDS-PAGE and N-terminal sequencing, under different processing conditions. TlAPA1 shared the highest identity of 70.3% with the aspartic endopeptidase from Byssochlamys spectabilis (GAD91729) and was classified into a new subgroup of the aspartic protease A1 family, based on evolutionary analysis. Mature TlAPA1 protein displayed an optimal activity at 60 °C and remained stable at temperatures of 55 °C and below, indicating the thermostable nature of TlAPA1 aspartic protease. During the auto-activation processing of proTlAPA1, a 45-kDa intermediate was identified that divided the processing mechanism into two steps: formation of intermediates and activation of the mature protein (TlAPA1). The former step can be processed without proteolytic activity, while the latter process depended on protease activity completely. The discovery of the novel aspartic protease TlAPA1 and the study of its activation process will contribute to a better understanding of the mechanism of aspartic protease auto-activation.
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A novel thermostable aspartic protease from Talaromyces leycettanus and its specific autocatalytic activation through an intermediate transition state
2019Co-Authors: Guo Yujie, Tu Tao, Yaxin Ren, Yaru Wang, Yingguo Bai, Su Xiaoyun, Wang Yuan, Bin Yao, Huoqing Huang, Huiying LuoAbstract:ABSTRACT Aspartic proteases exhibit optimum enzyme activity under acidic condition and have been extensively used in food, fermentation and leather industries. In this study, a novel aspartic protease precursor (proTlAPA1) from Talaromyces leycettanus was identified and successfully expressed in Pichia pastoris. Subsequently, the auto-activation processing of the zymogen proTlAPA1 was studied by SDS-PAGE and N-terminal sequencing, under different processing conditions. TlAPA1 shared the highest identity of 70.3 % with the aspartic endopeptidase from Byssochlamys spectabilis (GAD91729) and was classified into a new subgroup of the aspartic protease A1 family, based on evolutionary analysis. Mature TlAPA1 protein displayed an optimal activity at 60 °C and remained stable at temperatures of 55 °C and below, indicating the thermostable nature of TlAPA1 aspartic protease. During the auto-activation processing of proTlAPA1, a 45 kDa intermediate was identified that divided the processing mechanism into two steps: formation of intermediates, and activation of the mature protein (TlAPA1). The former step was completely induced by pH of the buffer, while the latter process depended on protease activity. The discovery of the novel aspartic protease TlAPA1 and study of its activation process will contribute to a better understanding of the mechanism of aspartic proteases auto-activation. IMPORTANCE The novel aspartic protease TlAPA1 was identified from T. leycettanus and expressed as a zymogen (proTlAPA1) in P. pastoris. Enzymatic characteristics of the mature protein were studied and the specific pattern of zymogen conversion was described. The auto-activation processing of proTlAPA1 proceeded in two stages and an intermediate was identified in this process. These results describe a new subgroup of aspartic protease A1 family and provide insights into a novel mode of activation processing in aspartic proteases.
