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Lott TT, Martin NH, Dumpler J, Wiedmann M, Moraru CI. Microbacterium represents an emerging microorganism of concern in microfiltered extended shelf-life milk products. J Dairy Sci 2023; 106:8434-8448. [PMID: 37678790 DOI: 10.3168/jds.2023-23734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Accepted: 07/13/2023] [Indexed: 09/09/2023]
Abstract
Growing interest in the manufacture of extended shelf-life (ESL) milk, which is typically achieved by a high-temperature treatment called ultra-pasteurization (UP), is driven by distribution challenges, efforts to reduce food waste, and more. Even though high-temperature, short-time (HTST) pasteurized milk has a substantially shorter shelf life than UP milk, HTST milk is preferred in the United States because consumers tend to perceive UP milk as less desirable due to the "cooked" flavor associated with high-temperature processing. While ESL beyond 21 d may be possible for HTST, the survival and outgrowth of psychrotolerant aerobic spore-forming bacteria can still be a limitation to extending shelf life of HTST milk. Microfiltration (MF) is effective for reducing vegetative microorganisms and spores in raw milk, but it is unclear what the effects of membrane pore size, storage temperature, and milk type (i.e., skim vs. whole) are on the microbial shelf life of milk processed by both MF and HTST pasteurization. To investigate these factors, raw skim milk was MF using different pore sizes (0.8 or 1.2 μm), and then MF skim milk and standardized whole milk (MF skim with heat-treated [85°C for 20 s] cream) were HTST pasteurized at 75°C for 20 s. Subsequently, milk was stored at 3°C, 6.5°C, or 10°C and total bacteria counts were measured for up to 63 d. An ANOVA indicated that mean bacterial concentrations between storage temperatures were significantly different from each other, with mean maximum observed concentrations of 3.67, 5.33, and 8.08 log10 cfu/mL for storage temperatures 3°C, 6.5°C, and 10°C, respectively. Additionally, a smaller difference in mean maximum bacterial concentrations throughout shelf life was identified between pore sizes (<1 log cfu/mL), but no significant difference was attributed to milk type. An unexpected outcome of this study was the identification of Microbacterium as a major contributor to the bacterial population in MF ESL milk. Microbacterium is a psychrotolerant, thermoduric gram-positive, non-spore-forming rod with a small cell size (∼0.9 μm length and ∼0.3 μm width), which our data suggest was able to permeate the membranes used in this study, survive HTST pasteurization, and then grow at refrigeration temperatures. While spores continue to be a key concern for the manufacture of MF, ESL milk, our study demonstrates the importance of other psychrotolerant, thermoduric bacteria such as Microbacterium to these products.
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Affiliation(s)
- T T Lott
- Department of Food Science, Cornell University, Ithaca, NY 14853
| | - N H Martin
- Department of Food Science, Cornell University, Ithaca, NY 14853.
| | - J Dumpler
- Department of Food Science, Cornell University, Ithaca, NY 14853
| | - M Wiedmann
- Department of Food Science, Cornell University, Ithaca, NY 14853
| | - C I Moraru
- Department of Food Science, Cornell University, Ithaca, NY 14853.
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Effects of extrusion specific mechanical energy and dryer conditions on the survival of Bacillus coagulans GBI-30, 6086 for commercial pet food applications. Anim Feed Sci Technol 2022. [DOI: 10.1016/j.anifeedsci.2022.115290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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3
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Bellassi P, Fontana A, Callegari ML, Cappa F, Morelli L. Microbacterium paulum sp. nov., isolated from microfiltered milk. Int J Syst Evol Microbiol 2021; 71. [PMID: 34807813 DOI: 10.1099/ijsem.0.005119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A novel Gram-stain-positive, strictly aerobic, short rod-shaped bacterium, designated 2CT, was isolated from freshly packaged microfiltered milk. This strain was able to grow within the NaCl concentration range of 0-5 % (w/v), temperature range of 8-37 °C (optimally at 30 °C) and at pH 6.0-10.0. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 2CT was closely related to species of the genus Microbacterium, with the highest sequence similarity (99.2 %) to Microbacterium lacticum DSM 20427T as well as Microbacterium flavum DSM 18909T (=YM18-098T). The phylogenetic tree based on 16S rRNA genes showed that strain 2CT clustered with M. flavum DSM 18909T. However, the phylogenetic tree based on concatenated 16S rRNA and four housekeeping genes showed that strain 2CT clustered with M. lacticum DSM 20427T. Furthermore, the phylogenomic tree showed that strain 2CT clustered with M. lacticum DSM 20427T and M. flavum DSM 18909T. The major respiratory quinones were MK-10, MK-11 and MK-12. The predominant cellular fatty acids were anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0. The polar lipid composition of strain 2CT consisted of diphosphatidylglycerol, phosphatidylglycerol, three unidentified glycolipids and two unidentified lipids. The cell-wall peptidoglycan type was a variant of B1α {Gly} [l-Lys] d-Glu-l-Lys, with the amino acids lysine, glycine, alanine and glutamic acid. The whole-cell sugars consisted of galactose, glucose, ribose and minor amounts of rhamnose. In addition, strain 2CT showed a glycolyl-type cell wall. The genomic DNA G+C content was 69.8mol%, while the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values with the closely related Microbacterium species were below the recognized thresholds of 95-96 % ANI and 70 % DDH for species definition. Based on the phenotypic and genotypic data, strain 2CT (=LMG 32277T=CECT 30329T) is considered to represent a new species, for which the name Microbacterium paulum sp. nov. is proposed.
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Affiliation(s)
- Paolo Bellassi
- Department for Sustainable Food Process (DiSTAS), Università Cattolica del Sacro Cuore, Piacenza, Italy
| | - Alessandra Fontana
- Department for Sustainable Food Process (DiSTAS), Università Cattolica del Sacro Cuore, Piacenza, Italy
| | - Maria Luisa Callegari
- Department for Sustainable Food Process (DiSTAS), Università Cattolica del Sacro Cuore, Piacenza, Italy
| | - Fabrizio Cappa
- Department for Sustainable Food Process (DiSTAS), Università Cattolica del Sacro Cuore, Piacenza, Italy
| | - Lorenzo Morelli
- Department for Sustainable Food Process (DiSTAS), Università Cattolica del Sacro Cuore, Piacenza, Italy
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Li TT, Feng LF, Gu XP, Zhang CL, Wang P, Hu GH. Intensification of Polymerization Processes by Reactive Extrusion. Ind Eng Chem Res 2021. [DOI: 10.1021/acs.iecr.0c05078] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Tian-Tian Li
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Lian-Fang Feng
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
- Institute of Zhejiang University−Quzhou, 78 Jiuhua Boulevard North, Quzhou, 324000, China
| | - Xue-Ping Gu
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
- Institute of Zhejiang University−Quzhou, 78 Jiuhua Boulevard North, Quzhou, 324000, China
| | - Cai-Liang Zhang
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
- Institute of Zhejiang University−Quzhou, 78 Jiuhua Boulevard North, Quzhou, 324000, China
| | - Pan Wang
- CNRS-Université de Lorraine, Laboratoire Réactions et Génie des Procédés (LRGP, CNRS UMR 7274), 1 rue Grandville, BP 20451, Nancy, 54001, France
| | - Guo-Hua Hu
- CNRS-Université de Lorraine, Laboratoire Réactions et Génie des Procédés (LRGP, CNRS UMR 7274), 1 rue Grandville, BP 20451, Nancy, 54001, France
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Bellassi P, Cappa F, Fontana A, Morelli L. Phenotypic and Genotypic Investigation of Two Representative Strains of Microbacterium Species Isolated From Micro-Filtered Milk: Growth Capacity and Spoilage-Potential Assessment. Front Microbiol 2020; 11:554178. [PMID: 33193134 PMCID: PMC7642513 DOI: 10.3389/fmicb.2020.554178] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 09/23/2020] [Indexed: 11/23/2022] Open
Abstract
The microbiota that spoil long-life micro-filtered milk generally includes species of the genus Microbacterium. The metabolic properties of this of microorganisms that could potentially modify the quality of micro-filtered milk are still unexplored when compared to better-known microorganisms, such as the spore-forming Bacillus and Paenibacillus spp., and Gram-negative contaminants, such as species of the genera Pseudomonas and Acinetobacter. In this preliminary study, two strains of Microbacterium (M. lacticum 18H and Microbacterium sp. 2C) isolated from micro-filtered milk were characterized in depth, both phenotypically and genotypically, to better understand their role in long-term milk spoilage. The study highlights the ability of these strains to produce high cell numbers and low acidification in micro-filtered milk under storage and shelf-life conditions. Phenotypic analyses of the two Microbacterium sp. isolates revealed that both strains have low proteolytic and lipolytic activity. In addition, they have the ability to form biofilms. This study aims to be a preliminary investigation of milk-adapted strains of the Microbacterium genus, which are able to grow to high cellular levels and perform slight but not negligible acidification that could pose a potential risk to the final quality of micro-filtered milk. Furthermore, M. lacticum 18H and Microbacterium sp. 2C were genotypically characterized in relation to the characteristics of interest in the milk environment. Some protein-encoding genes involved in lactose metabolism were found in the genomes, such as β-galactosidase, lactose permease, and L-lactate dehydrogenase. The phenotypically verified proteolytic ability was supported in the genomes by several genes that encode for proteases, peptidases, and peptide transferases.
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Affiliation(s)
- Paolo Bellassi
- Department for Sustainable Food Process (DiSTAS), Università Cattolica del Sacro Cuore, Piacenza, Italy
| | - Fabrizio Cappa
- Department for Sustainable Food Process (DiSTAS), Università Cattolica del Sacro Cuore, Piacenza, Italy.,Biotechnology Research Centre (CRB), Cremona, Italy
| | - Alessandra Fontana
- Department for Sustainable Food Process (DiSTAS), Università Cattolica del Sacro Cuore, Piacenza, Italy.,Biotechnology Research Centre (CRB), Cremona, Italy
| | - Lorenzo Morelli
- Department for Sustainable Food Process (DiSTAS), Università Cattolica del Sacro Cuore, Piacenza, Italy.,Biotechnology Research Centre (CRB), Cremona, Italy
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Leonard W, Zhang P, Ying D, Fang Z. Application of extrusion technology in plant food processing byproducts: An overview. Compr Rev Food Sci Food Saf 2019; 19:218-246. [PMID: 33319515 DOI: 10.1111/1541-4337.12514] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 10/21/2019] [Accepted: 11/08/2019] [Indexed: 12/29/2022]
Abstract
The food processing industry generates an immense amount of waste, which leads to major concerns for its environmental impact. However, most of these wastes, such as plant-derived byproducts, are still nutritionally adequate for use in food manufacturing. Extrusion is one of the most versatile and commercially successful processing technologies, with its widespread applications in the production of pasta, snacks, crackers, and meat analogues. It allows a high degree of user control over the processing parameters that significantly alters the quality of final products. This review features the past research on manufacture of extruded foods with integration of various plant food processing byproducts. The impact of extrusion parameters and adding various byproducts on the nutritional, physicochemical, sensory, and microbiological properties of food products are comprehensively discussed. This paper also provides fundamental knowledge and practical techniques for food manufacturers and researchers on the extrusion processing of plant food byproducts, which may increase economical return to the industry and reduce the environmental impact.
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Affiliation(s)
- William Leonard
- School of Agriculture and Food, The University of Melbourne, Parkville, Victoria, Australia
| | - Pangzhen Zhang
- School of Agriculture and Food, The University of Melbourne, Parkville, Victoria, Australia
| | - Danyang Ying
- CSIRO Agriculture & Food, Melbourne, Victoria, Australia
| | - Zhongxiang Fang
- School of Agriculture and Food, The University of Melbourne, Parkville, Victoria, Australia
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Wang H, Wilksch JJ, Chen L, Tan JWH, Strugnell RA, Gee ML. Influence of Fimbriae on Bacterial Adhesion and Viscoelasticity and Correlations of the Two Properties with Biofilm Formation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:100-106. [PMID: 27959542 DOI: 10.1021/acs.langmuir.6b03764] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The surface polymers of bacteria determine the ability of bacteria to adhere to a substrate for colonization, which is an essential step for a variety of microbial processes, such as biofilm formation and biofouling. Capsular polysaccharides and fimbriae are two major components on a bacterial surface, which are critical for mediating cell-surface interactions. Adhesion and viscoelasticity of bacteria are two major physical properties related to bacteria-surface interactions. In this study, we employed atomic force microscopy (AFM) to interrogate how the adhesion work and the viscoelasticity of a bacterial pathogen, Klebsiella pneumoniae, influence biofilm formation. To do this, the wild-type, type 3 fimbriae-deficient, and type 3 fimbriae-overexpressed K. pneumoniae strains have been investigated in an aqueous environment. The results show that the measured adhesion work is positively correlated to biofilm formation; however, the viscoelasticity is not correlated to biofilm formation. This study indicates that AFM-based adhesion measurements of bacteria can be used to evaluate the function of bacterial surface polymers in biofilm formation and to predict the ability of bacterial biofilm formation.
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Affiliation(s)
- Huabin Wang
- Chongqing Key Laboratory of Multi-Scale Manufacturing Technology, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences , Chongqing 400714, China
- Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences , Shanghai 201800, China
| | | | - Ligang Chen
- Chongqing Key Laboratory of Multi-Scale Manufacturing Technology, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences , Chongqing 400714, China
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Chen C, Chen L, Wang P, Wu LF, Song T. Magnetically-induced elimination of Staphylococcus aureus by magnetotactic bacteria under a swing magnetic field. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2016; 13:363-370. [PMID: 27562212 DOI: 10.1016/j.nano.2016.08.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 07/16/2016] [Accepted: 08/11/2016] [Indexed: 11/27/2022]
Abstract
This study aims to explore a therapeutic tool that kills pathogens by using mechanical force other than temperature. We fabricated a device that generates a swing magnetic field (sMF) with low-heat production and then evaluated the killing effect of magnetotactic bacteria MO-1 on Staphylococcus aureus (S. aureus) under the sMF. S. aureus was only killed under the sMF when attached to MO-1 cells. The killing efficiency increased with increasing attachment ratio of MO-1 cells to S. aureus. Treatment with antibody-coated MO-1 cells under the sMF improved the healing of S. aureus-infected wound. The theoretical analysis demonstrated that MO-1 cells generated a mechanical force of approximately 8kPa under the sMF, thereby exerting on S. aureus and inducing cell death. The proposed platform, which uses magnetotactic bacteria under the sMF to generate mechanical force, provides a basis for development of therapeutic tools to treat infectious diseases.
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Affiliation(s)
- Changyou Chen
- Beijing Key Laboratory of Bioelectromagnetism, Institute of Electrical Engineering, Chinese Academy of Sciences, No. 6 Bei'er Tiao Zhongguancun HaiDian, Beijing, 100190, China; University of Chinese Academy of Sciences, No.19A Yuquanlu, Beijing, 100049, China; France-China Bio-Mineralization and Nano-Structures Laboratory, No. 6 Bei'er Tiao Zhongguancun HaiDian, Beijing, 100190, China.
| | - Linjie Chen
- Beijing Key Laboratory of Bioelectromagnetism, Institute of Electrical Engineering, Chinese Academy of Sciences, No. 6 Bei'er Tiao Zhongguancun HaiDian, Beijing, 100190, China; University of Chinese Academy of Sciences, No.19A Yuquanlu, Beijing, 100049, China; France-China Bio-Mineralization and Nano-Structures Laboratory, No. 6 Bei'er Tiao Zhongguancun HaiDian, Beijing, 100190, China.
| | - Pingping Wang
- Beijing Key Laboratory of Bioelectromagnetism, Institute of Electrical Engineering, Chinese Academy of Sciences, No. 6 Bei'er Tiao Zhongguancun HaiDian, Beijing, 100190, China; France-China Bio-Mineralization and Nano-Structures Laboratory, No. 6 Bei'er Tiao Zhongguancun HaiDian, Beijing, 100190, China.
| | - Long-Fei Wu
- France-China Bio-Mineralization and Nano-Structures Laboratory, No. 6 Bei'er Tiao Zhongguancun HaiDian, Beijing, 100190, China; Laboratoire de Chimie Bactérienne, UMR7283, Aix-Marseille University, Institut de Microbiologie de la Méditerranée, CNRS, Marseille, France.
| | - Tao Song
- Beijing Key Laboratory of Bioelectromagnetism, Institute of Electrical Engineering, Chinese Academy of Sciences, No. 6 Bei'er Tiao Zhongguancun HaiDian, Beijing, 100190, China; University of Chinese Academy of Sciences, No.19A Yuquanlu, Beijing, 100049, China; France-China Bio-Mineralization and Nano-Structures Laboratory, No. 6 Bei'er Tiao Zhongguancun HaiDian, Beijing, 100190, China.
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Nair A, Maldonaldo J, Miyazawa Y, Cuitiño A, Schaffner D, Karwe M. Numerical simulation of stress distribution in heterogeneous solids during high pressure processing. Food Res Int 2016. [DOI: 10.1016/j.foodres.2016.03.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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10
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Lambertini E, Buchanan RL, Narrod C, Ford RM, Baker RC, Pradhan AK. Quantitative assessment of human and pet exposure to Salmonella associated with dry pet foods. Int J Food Microbiol 2016; 216:79-90. [DOI: 10.1016/j.ijfoodmicro.2015.09.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 07/17/2015] [Accepted: 09/05/2015] [Indexed: 10/23/2022]
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11
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Lambertini E, Buchanan RL, Narrod C, Pradhan AK. Transmission of Bacterial Zoonotic Pathogens between Pets and Humans: The Role of Pet Food. Crit Rev Food Sci Nutr 2015; 56:364-418. [DOI: 10.1080/10408398.2014.902356] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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12
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Lee Y. An evaluation of microbial and chemical contamination sources related to the deterioration of tap water quality in the household water supply system. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2013; 10:4143-60. [PMID: 24018837 PMCID: PMC3799508 DOI: 10.3390/ijerph10094143] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/08/2013] [Accepted: 08/21/2013] [Indexed: 11/27/2022]
Abstract
The predominant microorganisms in samples taken from shower heads in residences in the Korean city "N" were Stenotrophomonas maltophilia, Sphingomonas paucimobilis, Acidovorax temperans, and Microbacterium lacticum. Legionella was not detected in this case. The volatile organic compounds (VOCs) vinylacetate, NN-DMA, cis-1,2-dichloroethylene, epichlorohydrin, and styrene were measured in five types of plastic pipes: PVC, PB, PP, PE, and cPVC. The rate of multiplication of the heterotrophic plate count (HPC) attached on the copper pipe in contact with hot tap water was higher than the rate for the copper pipe in contact with cold tap water. Biofilm accumulation on stainless steel pipes with added acetate (3 mg/L) was 2.56 times higher than the non-supplemented condition. Therefore, the growth of HPC in the pipe system was affected by the type and availability of nutrients and depended on variables such as heating during the hot water supply.
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Affiliation(s)
- Yoonjin Lee
- Department of General Education, Konyang University, 121 Daehakro, Nonsan, Chungnam 320-711, Korea.
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Ukuku DO, Mukhopadhyay S, Onwulata C. Effect of Storage Temperature on Survival and Recovery of Thermal and Extrusion InjuredEscherichia coliK-12 in Whey Protein Concentrate and Corn Meal. Foodborne Pathog Dis 2013; 10:62-8. [DOI: 10.1089/fpd.2012.1269] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Dike O. Ukuku
- Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania
| | - Sudarsan Mukhopadhyay
- Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania
| | - Charles Onwulata
- Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania
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Kalashnikov M, Lee JC, Campbell J, Sharon A, Sauer-Budge AF. A microfluidic platform for rapid, stress-induced antibiotic susceptibility testing of Staphylococcus aureus. LAB ON A CHIP 2012; 12:4523-32. [PMID: 22968495 PMCID: PMC3489182 DOI: 10.1039/c2lc40531h] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The emergence and spread of bacterial resistance to ever increasing classes of antibiotics intensifies the need for fast phenotype-based clinical tests for determining antibiotic susceptibility. Standard susceptibility testing relies on the passive observation of bacterial growth inhibition in the presence of antibiotics. In this paper, we present a novel microfluidic platform for antibiotic susceptibility testing based on stress-activation of biosynthetic pathways that are the primary targets of antibiotics. We chose Staphylococcus aureus (S. aureus) as a model system due to its clinical importance, and we selected bacterial cell wall biosynthesis as the primary target of both stress and antibiotic. Enzymatic and mechanical stresses were used to damage the bacterial cell wall, and a β-lactam antibiotic interfered with the repair process, resulting in rapid cell death of strains that harbor no resistance mechanism. In contrast, resistant bacteria remained viable under the assay conditions. Bacteria, covalently-bound to the bottom of the microfluidic channel, were subjected to mechanical shear stress created by flowing culture media through the microfluidic channel and to enzymatic stress with sub-inhibitory concentrations of the bactericidal agent lysostaphin. Bacterial cell death was monitored via fluorescence using the Sytox Green dead cell stain, and rates of killing were measured for the bacterial samples in the presence and absence of oxacillin. Using model susceptible (Sanger 476) and resistant (MW2) S. aureus strains, a metric was established to separate susceptible and resistant staphylococci based on normalized fluorescence values after 60 min of exposure to stress and antibiotic. Because this ground-breaking approach is not based on standard methodology, it circumvents the need for minimum inhibitory concentration (MIC) measurements and long wait times. We demonstrate the successful development of a rapid microfluidic-based and stress-activated antibiotic susceptibility test by correctly designating the phenotypes of 16 additional clinically relevant S. aureus strains in a blinded study. In addition to future clinical utility, this method has great potential for studying the effects of various stresses on bacteria and their antibiotic susceptibility.
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Affiliation(s)
- Maxim Kalashnikov
- Center for Manufacturing Innovation, Fraunhofer USA, Brookline, Massachusetts 02446, USA
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Abstract
AbstractThe present review describes the influence of different types of mixing systems under excess turbulence conditions on microorganisms. Turbohypobiosis phenomena were described by applying a method for measurement of the kinetic energy of flow fluctuations based on the piezoeffect. It can be assumed that the shear stress effect (the state of turbohypobiosis) plays a role mainly when alternative mechanisms in cells cannot ensure a normal physiological state under stress conditions. Practically any system (inner construction of a bioreactor, culture and cultivation conditions, including mixing) requires its own optimisation to achieve the final goal, namely, the maximum product and/or biomass yields from substrate (YP/S or/and YX/S), respectively. Data on the biotechnological performance of cultivation as well as power input, kinetic energy (e) of flow fluctuations, air consumption rate, rotational speed, tip speed, etc. do not correlate directly if the mixing systems (impellers-baffles) are dissimilar. Even the widely used specific power consumption cannot be relied upon for scaling up the cultivation performance using dissimilar mixing systems. A biochemical explanation for substrate and product transport via cell walls, carbon pathways, energy generation and utilisation, etc. furnishes insight into cellular interactions with turbulence of different origin for different types of microorganisms (single cells, mycelia forming cells, etc.).
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Gregson CM, Lee TC. Quality Modification of Food by Extrusion Processing. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2004; 542:187-200. [PMID: 15174581 DOI: 10.1007/978-1-4419-9090-7_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Christopher M Gregson
- Department of Food Science, Center for Advanced Food Technology, Rutgers University, 65 Dudley Road, New Brunswick, New Jersey 08901, USA
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