1
|
Estes Bright LM, Chug MK, Thompson S, Brooks M, Brisbois EJ, Handa H. Analysis of the broad-spectrum potential of nitric oxide for antibacterial activity against clinically isolated drug-resistant bacteria. J Biomed Mater Res B Appl Biomater 2024; 112:e35442. [PMID: 38923117 DOI: 10.1002/jbm.b.35442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 04/18/2024] [Accepted: 06/09/2024] [Indexed: 06/28/2024]
Abstract
The development of drug-resistant microorganisms is taking a heavy toll on the biomedical world. Clinical infections are costly and becoming increasingly dangerous as bacteria that once responded to standard antibiotic treatment are developing resistance mechanisms that require innovative treatment strategies. Nitric oxide (NO) is a gaseous molecule produced endogenously that has shown potent antibacterial capabilities in numerous research studies. Its multimechanistic antibacterial methods prevent the development of resistance and have shown potential as an alternative to antibiotics. However, there has yet to be a direct comparison study evaluating the antibacterial properties of NO against antibiotic susceptible and antibiotic-resistant clinically isolated bacterial strains. Herein, standardized lab and clinically isolated drug-resistant bacterial strains are compared side-by-side for growth and viability following treatment with NO released from S-nitrosoglutathione (GSNO), an NO donor molecule. Evaluation of growth kinetics revealed complete killing of E. coli lab and clinical strains at 17.5 mM GSNO, though 15 mM displayed >50% killing and significantly reduced metabolic activity, with greater dose dependence for membrane permeability. Clinical P. aeruginosa showed greater susceptibility to GSNO during growth curve studies, but metabolic activity and membrane permeability demonstrated similar effects for 12.5 mM GSNO treatment of lab and clinical strains. MRSA lab and clinical strains exhibited total killing at 17.5 mM treatment, though metabolic activity was decreased, and membrane permeation began at 12.5 mM for both strains. Lastly, both S. epidermidis strains were killed by 15 mM GSNO, with sensitivities in metabolic activity and membrane permeability at 12.5 mM GSNO. The mirrored antibacterial effects seen by the lab and clinical strains of two Gram-negative and two Gram-positive bacteria reveal the translational success of NO as an antibacterial therapy and potential alternative to standard antibiotic treatment.
Collapse
Affiliation(s)
- Lori M Estes Bright
- School of Chemical, Materials, and Biomedical Engineering, College of Engineering, University of Georgia, Athens, Georgia, USA
| | - Manjyot Kaur Chug
- School of Chemical, Materials, and Biomedical Engineering, College of Engineering, University of Georgia, Athens, Georgia, USA
| | - Stephen Thompson
- School of Chemical, Materials, and Biomedical Engineering, College of Engineering, University of Georgia, Athens, Georgia, USA
| | - Megan Brooks
- School of Chemical, Materials, and Biomedical Engineering, College of Engineering, University of Georgia, Athens, Georgia, USA
| | - Elizabeth J Brisbois
- School of Chemical, Materials, and Biomedical Engineering, College of Engineering, University of Georgia, Athens, Georgia, USA
| | - Hitesh Handa
- School of Chemical, Materials, and Biomedical Engineering, College of Engineering, University of Georgia, Athens, Georgia, USA
- Pharmaceutical and Biomedical Sciences Department, College of Pharmacy, University of Georgia, Athens, Georgia, USA
| |
Collapse
|
2
|
Kilonzi JM, Otieno S. Degradation kinetics and physiological studies of organophosphates degrading microorganisms for soil bioremediation. STRESS BIOLOGY 2024; 4:11. [PMID: 38319394 PMCID: PMC10847075 DOI: 10.1007/s44154-023-00138-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 11/15/2023] [Indexed: 02/07/2024]
Abstract
Organophosphate compounds are widely used in agricultural activities to optimize food production. Contamination of field soil by these compounds may result in detrimental effects on soil biota. The aim of the present study was to isolate microorganisms from field soils and evaluate the strains on ability to degrade organophosphates as single isolate and as a consortium. Isolated strains were identified using both biochemical and molecular techniques. Results revealed that, out of the 46 isolated strains, three isolates herein referred to as S6, S36 and S37 showed an average diazinon degradation rate of 76.4%, 76.7% and 76.8% respectively, of the initial dose (50 ppm) within 11 days of incubation in mineral medium. Notably, isolates S36 and S37 were more effective than S6 in degrading diazinon by 40% in soil aliquot after 11 days and therefore were evaluated on biochemical reactions and molecular identification. The isolates showed variable biochemical characteristics. However, both isolates possessed catalase enzyme, but lacked oxidase enzyme. Molecular characterization showed that, the closest species for S36 and S37 were Priestia megaterium and P. arybattia, respectively, based on 16S rRNA gene similarity (> 99%). Combination of the strains increased diazinon degradation ability by 45% compared to single strain treatment. Chlorpyrifos was the most highly degraded organophosphate, compared to phorate and cadusafos. Therefore it is expected that the pesticide-degrading bacteria could be a solution to soil health improvement and contribution to the production of safe agricultural products.
Collapse
Affiliation(s)
- J M Kilonzi
- Kenya Agricultural and Livestock Research Organization Tigoni, Limuru, P.O BOX 338-0217, Kenya.
| | - S Otieno
- Kenya Agricultural and Livestock Research Organization Tigoni, Limuru, P.O BOX 338-0217, Kenya
| |
Collapse
|
3
|
Zheng A, Liu J, Wang M, Bu N, Liu D, Wei C. Footprint analysis of CO 2 in microbial community succession of raw milk and assessment of its quality. Front Nutr 2023; 10:1285653. [PMID: 38192649 PMCID: PMC10773745 DOI: 10.3389/fnut.2023.1285653] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Accepted: 11/29/2023] [Indexed: 01/10/2024] Open
Abstract
With the growing production of raw milk, interest has been increasing in its quality control. CO2, as a cold processing additive, has been studied to extend the cold storage period and improve the quality of raw milk. However, it is yet uncertain how representative microbial species and biomarkers can succeed one another at distinct critical periods during refrigeration. Therefore, the effects of CO2 treatment on the succession footprint of the microbial community and changes in quality during the period of raw milk chilling were examined by 16S rRNA analysis combined with electronic nose, and electronic tongue techniques. The results indicated that, the refrigeration time was shown to be prolonged by CO2 in a concentration-dependent way. And CO2 treatment was linked to substantial variations in beta and alpha diversity as well as the relative abundances of various microbial taxa (p < 0.01). The dominant bacterial phylum Proteobacteria was replaced with Firmicutes, while the major bacterial genera Acinetobacter and Pseudomonas were replaced with lactic acid bacteria (LAB), including Leuconostoc, Lactococcus, and Lactobacillus. From the perspective of biomarkers enriched in CO2-treated sample, almost all of them belong to LAB, no introduction of harmful toxins has been found. The assessment of the quality of raw milk revealed that CO2 improved the quality of raw milk by lowering the acidity and the rate of protein and fat breakdown, and improved the flavor by reducing the generation of volatiles, and increasing umami, richness, milk flavor and sweetness, but reducing sourness. These findings offer a new theoretical foundation for the industrial use of CO2 in raw milk.
Collapse
Affiliation(s)
- Anran Zheng
- School of Animal Science and Technology, Ningxia University, Yinchuan, China
| | - Jun Liu
- School of Animal Science and Technology, Ningxia University, Yinchuan, China
- School of Life Science, Hubei Normal University, Huangshi, China
| | - Mengsong Wang
- School of Food Science and Engineering, Ningxia University, Yinchuan, China
| | - Ningxia Bu
- School of Animal Science and Technology, Ningxia University, Yinchuan, China
| | - Dunhua Liu
- School of Animal Science and Technology, Ningxia University, Yinchuan, China
- School of Food Science and Engineering, Ningxia University, Yinchuan, China
| | - Chaokun Wei
- School of Food Science and Engineering, Ningxia University, Yinchuan, China
| |
Collapse
|
4
|
Schalli M, Platzer S, Schmutz R, Ofner-Kopeinig P, Reinthaler FF, Haas D. Dissolved Carbon Dioxide: The Lifespan of Staphylococcus aureus and Enterococcus faecalis in Bottled Carbonated Mineral Water. BIOLOGY 2023; 12:biology12030432. [PMID: 36979124 PMCID: PMC10045048 DOI: 10.3390/biology12030432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 03/07/2023] [Accepted: 03/09/2023] [Indexed: 03/16/2023]
Abstract
During the process of mineral water production, many possible contamination settings can influence the quality of bottled water. Microbial contamination can originate from different sources, for example, the ambient air, the bottles, the caps, and from the bottling machine itself. The aim of this study was to investigate the influence of three different carbon dioxide (CO2) concentrations (3.0 g/L, 5.5 g/L, and 7.0 g/L; 20 bottles each) in bottled mineral water on the bacterial growth of Staphylococcus aureus (S. aureus) and Enterococcus faecalis (Ent. faecalis). The examined mineral water was artificially contaminated before capping the bottles inside the factory. After a specific number of days, water samples were taken from freshly opened bottles and after filtration (100 mL), filters were placed on Columbia Agar with 5% Sheep blood to cultivate S. aureus and Slanetz and Bartley Agar to cultivate Ent. faecalis. The respective colony-forming units (CFU) were counted after incubation times ranging from 24 to 120 h. Colony-forming units of S. aureus were not detectable after the 16th and 27th day, whereas Ent. faecalis was not cultivable after the 5th and 13th day when stored inside the bottles. The investigation of the bottles that were stored open for a certain amount of time with CO2 bubbling out showed only single colonies for S. aureus after the 5th day and no CFUs for Ent. faecalis after the 17th day. A reduction in the two investigated bacterial strains during storage in carbonated mineral water bottles means that a proper standardized disinfection and cleaning procedure, according to valid hygiene standards of industrial bottling machines, cannot be replaced by carbonation.
Collapse
Affiliation(s)
- Michael Schalli
- Department for Water-Hygiene and Micro-Ecology, D&R Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, 8010 Graz, Austria
- Correspondence: ; Tel.: +43-316-385-73610
| | - Sabine Platzer
- Department for Water-Hygiene and Micro-Ecology, D&R Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, 8010 Graz, Austria
| | - Rainer Schmutz
- Department for Water-Hygiene and Micro-Ecology, D&R Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, 8010 Graz, Austria
| | - Petra Ofner-Kopeinig
- Institute for Medical Informatics, Statistics and Documentation, Medical University of Graz, 8010 Graz, Austria
| | - Franz F. Reinthaler
- Department for Water-Hygiene and Micro-Ecology, D&R Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, 8010 Graz, Austria
| | - Doris Haas
- Applied Hygiene and Aerobiology, D&R Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, 8010 Graz, Austria
| |
Collapse
|
5
|
Dixon B, Sui C, Briley A, Hsu PC, Howell C. Continuous, Nondestructive Detection of Microorganism Growth at Buried Interfaces with Vascularized Polymers. ACS APPLIED BIO MATERIALS 2023; 6:519-528. [PMID: 36633595 DOI: 10.1021/acsabm.2c00837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Evaluating surface bacterial growth at buried interfaces can be problematic due to the difficulties associated with obtaining samples. In this work, we present a new method to detect signals from microorganisms at buried interfaces that is nondestructive and can be conducted continuously. Inspired by vascular systems in nature that permit chemical communication between the surface and underlying tissues of an organism, we created a system in which an inert carrier fluid could be introduced into an empty vascular network embedded in a polymer matrix. When a microorganism layer was grown on top, small molecules produced by the growth process would diffuse down into the carrier fluid, which could then be collected and analyzed. We used this system to nondestructively detect signals from a surface layer of Escherichia coli using conductivity, ultraviolet-visible (UV-vis) absorbance spectroscopy, and high-performance liquid chromatography (HPLC) for organic acids, methods that ranged in sensitivity, time-to-result, and cost. Carrier fluid from sample vascularized polymers with surface bacterial growth recorded significantly higher values in both conductivity and absorbance at 350 nm compared to controls with no bacteria after 24 h. HPLC analysis showed three clear peaks that varied between the samples with bacteria and the controls without. Tests tracking the change in signals over 48 h showed clear trends that matched the bacterial growth curves, demonstrating the system's ability to monitor changes over time. A 2D finite element model of the system closely matched the experimental results, confirming the predictability of the system. Finally, tests using clinically relevant Staphylococcus aureus and Pseudomonas aeruginosa yielded differences in conductivity, absorbance, and HPLC peak areas unique to each species. This work lays the foundation for the use of vascularized polymers as an adaptive system for the continuous, nondestructive detection of surface microorganisms at buried interfaces in both industry and medicine.
Collapse
Affiliation(s)
- Brandon Dixon
- Department of Chemical and Biomedical Engineering, University of Maine, Orono, Maine04469, United States
| | - Chenxi Sui
- Thomas Lord Department of Mechanical Engineering and Material Science, Duke University, Durham, North Carolina27708, United States
| | - Anna Briley
- Department of Chemical and Biomedical Engineering, University of Maine, Orono, Maine04469, United States
| | - Po-Chun Hsu
- Thomas Lord Department of Mechanical Engineering and Material Science, Duke University, Durham, North Carolina27708, United States.,Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois60637, United States
| | - Caitlin Howell
- Department of Chemical and Biomedical Engineering, University of Maine, Orono, Maine04469, United States.,Graduate School of Biomedical Science and Engineering, University of Maine, Orono, Maine04469, United States
| |
Collapse
|
6
|
Esmaeilian S, Rotabakk BT, Lerfall J, Jakobsen AN, Abel N, Sivertsvik M, Olsen A. The use of soluble gas stabilization technology on food – A review. Trends Food Sci Technol 2021. [DOI: 10.1016/j.tifs.2021.09.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
|
7
|
Ultrasonic-assisted supercritical CO2 inactivation of bacterial spores and effect on the physicochemical properties of oil-in-water emulsions. J Supercrit Fluids 2021. [DOI: 10.1016/j.supflu.2021.105246] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
8
|
Abstract
Traditional sour beers are produced by spontaneous fermentations involving numerous yeast and bacterial species. One of the traits that separates sour beers from ales and lagers is the high concentration of organic acids such as lactic acid and acetic acid, which results in reduced pH and increased acidic taste. Several challenges complicate the production of sour beers through traditional methods. These include poor process control, lack of consistency in product quality, and lengthy fermentation times. This review summarizes the methods for traditional sour beer production with a focus on the use of lactobacilli to generate this beverage. In addition, the review describes the use of selected pure cultures of microorganisms with desirable properties in conjunction with careful application of processing steps. Together, this facilitates the production of sour beer with a higher level of process control and more rapid fermentation compared to traditional methods.
Collapse
|
9
|
Cantera S, Phandanouvong-Lozano V, Pascual C, García-Encina PA, Lebrero R, Hay A, Muñoz R. A systematic comparison of ectoine production from upgraded biogas using Methylomicrobium alcaliphilum and a mixed haloalkaliphilic consortium. WASTE MANAGEMENT (NEW YORK, N.Y.) 2020; 102:773-781. [PMID: 31812092 DOI: 10.1016/j.wasman.2019.11.043] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 11/20/2019] [Accepted: 11/26/2019] [Indexed: 05/12/2023]
Abstract
Biogas is the byproduct of anaerobic digestion with the highest valorization potential, however its full exploitation is limited by the lack of tax incentives and the inherent presence of pollutants. The development of technologies for biogas conversion into added-value products is crucial in order to ensure the competitiveness of this bioresource. This study constitutes the first proof of concept of upgraded biogas bioconversion into the high profit margin product ectoine. Ectoine represents the most expensive product synthesized by microorganisms with a retail value of 1000 $ kg-1 and a yearly increasing demand that currently entails a total market opportunity of 15000 M€. First, the production of ectoine from upgraded biogas was assessed in batch bioreactors. The presence of H2S did not exert a negative effect on the growth of the haloalkaliphilic ectoine producers, and ectoine yields up to 49 mg g biomass-1 were obtained. A second experiment conducted in continuous bubble column bioreactors confirmed the feasibility of the process under continuous mode (with ectoine yields of 109 mg g biomass-1). Finally, this study revealed that the removal of toxic compounds (i.e. medium dilution rate of 0.5 day-1) and process operation with a consortium composed of methylotrophic/non-methylotrophic ectoine producers enhanced upgraded biogas bioconversion. This research discloses the basis for the application of this innovative technology and could boost the economic performance of anaerobic digestion.
Collapse
Affiliation(s)
- Sara Cantera
- Laboratory of Microbiology, Wageningen University and Research Center, The Netherlands
| | | | - Celia Pascual
- Department of Chemical Engineering and Environmental Technology, Universidad de Valladolid, Dr. Mergelina, s/n, Valladolid, Spain; Institute of Sustainable Processes, Universidad de Valladolid, Spain
| | - Pedro A García-Encina
- Department of Chemical Engineering and Environmental Technology, Universidad de Valladolid, Dr. Mergelina, s/n, Valladolid, Spain; Institute of Sustainable Processes, Universidad de Valladolid, Spain
| | - Raquel Lebrero
- Department of Chemical Engineering and Environmental Technology, Universidad de Valladolid, Dr. Mergelina, s/n, Valladolid, Spain; Institute of Sustainable Processes, Universidad de Valladolid, Spain
| | - Anthony Hay
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA
| | - Raúl Muñoz
- Department of Chemical Engineering and Environmental Technology, Universidad de Valladolid, Dr. Mergelina, s/n, Valladolid, Spain; Institute of Sustainable Processes, Universidad de Valladolid, Spain.
| |
Collapse
|
10
|
Park DH. Effects of carbon dioxide on metabolite production and bacterial communities during kimchi fermentation. Biosci Biotechnol Biochem 2018; 82:1234-1242. [PMID: 29685096 DOI: 10.1080/09168451.2018.1459462] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Bacterial communities and metabolites in kimchi fermented under conventional conditions (CC) compared to CO2-rich environments (CO2) were analyzed. After a 20-day fermentation, lactic and acetic acid productions were 54 and 69 mM under CC, and 19 and 12 mM under CO2, respectively. The final pH of kimchi fermented under CC (CC-fermenting) and CO2 (CO2-fermenting) were 4.1 and 4.7, respectively. For bacterial communities, OTU and Chao1 indices were both 35 in fresh kimchi, 10 and 15 in CC-fermenting kimchi, and 8 and 24 in CO2-fermenting kimchi, respectively. Shannon and Simpson indices were 3.47 and 0.93 in fresh kimchi, 1.87-0.06 and 0.46-0.01 in CC-fermenting kimchi, and 1.65-0.44 and 0.63-0.12 in CO2-fermenting kimchi, respectively. Non-lactic acid bacteria were eliminated in fermenting kimchi after 12 days under CC and 6 days under CO2. I conclude that carbon dioxide can alter bacterial communities, reduce metabolite production, and improve fermented kimchi quality.
Collapse
Affiliation(s)
- Doo Hyun Park
- a Department of Nano Convergence , Seokyeong University , Seoul , Korea
| |
Collapse
|
11
|
Bergsveinson J, Redekop A, Zoerb S, Ziola B. Dissolved Carbon Dioxide Selects for Lactic Acid Bacteria Able to Grow in and Spoil Packaged Beer. JOURNAL OF THE AMERICAN SOCIETY OF BREWING CHEMISTS 2018. [DOI: 10.1094/asbcj-2015-0726-01] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Jordyn Bergsveinson
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK S7N 0W8, Canada
| | - Anna Redekop
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK S7N 0W8, Canada
| | - Sheree Zoerb
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK S7N 0W8, Canada
| | - Barry Ziola
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK S7N 0W8, Canada
| |
Collapse
|
12
|
Adhikari BM, Truong T, Bansal N, Bhandari B. Use of gases in dairy manufacturing: A review. Crit Rev Food Sci Nutr 2017; 58:2557-2569. [DOI: 10.1080/10408398.2017.1333488] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Bhaskar Mani Adhikari
- School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Australia
| | - Tuyen Truong
- School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Australia
| | - Nidhi Bansal
- School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Australia
| | - Bhesh Bhandari
- School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Australia
| |
Collapse
|
13
|
Lo R, Turner MS, Weeks M, Bansal N. Culture-independent bacterial community profiling of carbon dioxide treated raw milk. Int J Food Microbiol 2016; 233:81-89. [DOI: 10.1016/j.ijfoodmicro.2016.06.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 05/30/2016] [Accepted: 06/14/2016] [Indexed: 01/14/2023]
|
14
|
Lo R, Xue T, Weeks M, Turner MS, Bansal N. Inhibition of bacterial growth in sweet cheese whey by carbon dioxide as determined by culture-independent community profiling. Int J Food Microbiol 2015; 217:20-8. [PMID: 26476573 DOI: 10.1016/j.ijfoodmicro.2015.10.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 09/25/2015] [Accepted: 10/03/2015] [Indexed: 01/08/2023]
Abstract
Whey is a valuable co-product from cheese making that serves as a raw material for a wide range of products. Its rich nutritional content lends itself to rapid spoilage, thus it typically needs to be pasteurised and refrigerated promptly. Despite the extensive literature on milk spoilage bacteria, little is known about the spoilage bacteria of whey. The utility of carbon dioxide (CO2) to extend the shelf-life of raw milk and cottage cheese has been well established, but its application in whey preservation has not yet been explored. This study aims to characterise the microbial populations of fresh and spoiled sweet whey by culture-independent community profiling using 454 pyrosequencing of 16S rRNA gene amplicons and to determine whether carbonation is effective in inhibiting bacterial growth in sweet whey. The microbiota of raw Cheddar and Mozzarella whey was dominated by cheese starter bacteria. After pasteurisation, two out of the three samples studied became dominated by diverse environmental bacteria from various phyla, with Proteobacteria being the most dominant. Diverse microbial profiles were maintained until spoilage occurred, when the entire population was dominated by just one or two genera. Whey spoilage bacteria were found to be similar to those of milk. Pasteurised Cheddar and Mozzarella whey was spoiled by Bacillus sp. or Pseudomonas sp., and raw Mozzarella whey was spoiled by Pseudomonas sp., Serratia sp., and other members of the Enterobacteriaceae family. CO2 was effective in inhibiting bacterial growth of pasteurised Cheddar and Mozzarella whey stored at 15°C and raw Mozzarella whey stored at 4°C. The spoilage bacteria of the carbonated samples were similar to those of the non-carbonated controls.
Collapse
Affiliation(s)
- Raquel Lo
- School of Agriculture and Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Tian Xue
- School of Agriculture and Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Mike Weeks
- Dairy Innovation Australia Limited, Werribee, VIC 3030, Australia
| | - Mark S Turner
- School of Agriculture and Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia; Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Nidhi Bansal
- School of Agriculture and Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia.
| |
Collapse
|
15
|
Carbon monoxide as a metabolic energy source for extremely halophilic microbes: implications for microbial activity in Mars regolith. Proc Natl Acad Sci U S A 2015; 112:4465-70. [PMID: 25831529 DOI: 10.1073/pnas.1424989112] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Carbon monoxide occurs at relatively high concentrations (≥800 parts per million) in Mars' atmosphere, where it represents a potentially significant energy source that could fuel metabolism by a localized putative surface or near-surface microbiota. However, the plausibility of CO oxidation under conditions relevant for Mars in its past or at present has not been evaluated. Results from diverse terrestrial brines and saline soils provide the first documentation, to our knowledge, of active CO uptake at water potentials (-41 MPa to -117 MPa) that might occur in putative brines at recurrent slope lineae (RSL) on Mars. Results from two extremely halophilic isolates complement the field observations. Halorubrum str. BV1, isolated from the Bonneville Salt Flats, Utah (to our knowledge, the first documented extremely halophilic CO-oxidizing member of the Euryarchaeota), consumed CO in a salt-saturated medium with a water potential of -39.6 MPa; activity was reduced by only 28% relative to activity at its optimum water potential of -11 MPa. A proteobacterial isolate from hypersaline Mono Lake, California, Alkalilimnicola ehrlichii MLHE-1, also oxidized CO at low water potentials (-19 MPa), at temperatures within ranges reported for RSL, and under oxic, suboxic (0.2% oxygen), and anoxic conditions (oxygen-free with nitrate). MLHE-1 was unaffected by magnesium perchlorate or low atmospheric pressure (10 mbar). These results collectively establish the potential for microbial CO oxidation under conditions that might obtain at local scales (e.g., RSL) on contemporary Mars and at larger spatial scales earlier in Mars' history.
Collapse
|
16
|
Singh P, Gandhi N. Milk Preservatives and Adulterants: Processing, Regulatory and Safety Issues. FOOD REVIEWS INTERNATIONAL 2015. [DOI: 10.1080/87559129.2014.994818] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
17
|
Ongeng D, Geeraerd AH, Springael D, Ryckeboer J, Muyanja C, Mauriello G. Fate ofEscherichia coliO157:H7 andSalmonella entericain the manure-amended soil-plant ecosystem of fresh vegetable crops: A review. Crit Rev Microbiol 2013; 41:273-94. [DOI: 10.3109/1040841x.2013.829415] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
|
18
|
Vriesekoop F, Krahl M, Hucker B, Menz G. 125thAnniversary Review: Bacteria in brewing: The good, the bad and the ugly. JOURNAL OF THE INSTITUTE OF BREWING 2013. [DOI: 10.1002/jib.49] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Frank Vriesekoop
- Department of Food Science and Agri-Food Supply Chain Management; Harper Adams University; Newport TF10 8NB UK
- School of Health Sciences; University of Ballarat; Ballarat Victoria Australia
| | | | - Barry Hucker
- School of Health Sciences; University of Ballarat; Ballarat Victoria Australia
| | - Garry Menz
- School of Health Sciences; University of Ballarat; Ballarat Victoria Australia
- Carlton and United Breweries; Yatala Brewery; Yatala Queensland Australia
| |
Collapse
|
19
|
Corey A, Migone TS, Bolmer S, Fiscella M, Ward C, Chen C, Meister G. Bacillus anthracis protective antigen kinetics in inhalation spore-challenged untreated or levofloxacin/ raxibacumab-treated New Zealand white rabbits. Toxins (Basel) 2013; 5:120-38. [PMID: 23344456 PMCID: PMC3564073 DOI: 10.3390/toxins5010120] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 09/29/2012] [Accepted: 12/17/2012] [Indexed: 11/26/2022] Open
Abstract
Inhaled Bacillus anthracis spores germinate and the subsequent vegetative growth results in bacteremia and toxin production. Anthrax toxin is tripartite: the lethal factor and edema factor are enzymatic moieties, while the protective antigen (PA) binds to cell receptors and the enzymatic moieties. Antibiotics can control B. anthracis bacteremia, whereas raxibacumab binds PA and blocks lethal toxin effects. This study assessed plasma PA kinetics in rabbits following an inhaled B. anthracis spore challenge. Additionally, at 84 h post-challenge, 42% of challenged rabbits that had survived were treated with either levofloxacin/placebo or levofloxacin/raxibacumab. The profiles were modeled using a modified Gompertz/second exponential growth phase model in untreated rabbits, with added monoexponential PA elimination in treated rabbits. Shorter survival times were related to a higher plateau and a faster increase in PA levels. PA elimination half-lives were 10 and 19 h for the levofloxacin/placebo and levofloxacin/raxibacumab groups, respectively, with the difference attributable to persistent circulating PA-raxibacumab complex. PA kinetics were similar between untreated and treated rabbits, with one exception: treated rabbits had a plateau phase nearly twice as long as that for untreated rabbits. Treated rabbits that succumbed to disease had higher plateau PA levels and shorter plateau duration than surviving treated rabbits.
Collapse
MESH Headings
- Adjuvants, Immunologic/administration & dosage
- Administration, Inhalation
- Animals
- Anthrax/immunology
- Anthrax/mortality
- Anthrax/prevention & control
- Anthrax Vaccines/administration & dosage
- Anthrax Vaccines/immunology
- Anti-Bacterial Agents/pharmacology
- Antibodies, Monoclonal/pharmacology
- Antibodies, Monoclonal, Humanized
- Antigens, Bacterial/administration & dosage
- Antigens, Bacterial/immunology
- Antigens, Bacterial/metabolism
- Bacillus anthracis/immunology
- Bacterial Toxins/immunology
- Disease Models, Animal
- Female
- Kinetics
- Levofloxacin
- Male
- Ofloxacin/pharmacology
- Rabbits
- Spores, Bacterial/immunology
- Survival Analysis
Collapse
Affiliation(s)
- Alfred Corey
- Human Genome Sciences, Inc., 14200 Shady Grove Road, Rockville, MD 20850, USA; E-Mails: (T.-S.M.); (S.B.); (M.F.); (C.W.); (C.C.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-919-483-7032; Fax: +1-919-483-7032
| | - Thi-Sau Migone
- Human Genome Sciences, Inc., 14200 Shady Grove Road, Rockville, MD 20850, USA; E-Mails: (T.-S.M.); (S.B.); (M.F.); (C.W.); (C.C.)
| | - Sally Bolmer
- Human Genome Sciences, Inc., 14200 Shady Grove Road, Rockville, MD 20850, USA; E-Mails: (T.-S.M.); (S.B.); (M.F.); (C.W.); (C.C.)
| | - Michele Fiscella
- Human Genome Sciences, Inc., 14200 Shady Grove Road, Rockville, MD 20850, USA; E-Mails: (T.-S.M.); (S.B.); (M.F.); (C.W.); (C.C.)
| | - Chris Ward
- Human Genome Sciences, Inc., 14200 Shady Grove Road, Rockville, MD 20850, USA; E-Mails: (T.-S.M.); (S.B.); (M.F.); (C.W.); (C.C.)
| | - Cecil Chen
- Human Genome Sciences, Inc., 14200 Shady Grove Road, Rockville, MD 20850, USA; E-Mails: (T.-S.M.); (S.B.); (M.F.); (C.W.); (C.C.)
| | - Gabriel Meister
- Battelle Biomedical Research Center, 505 King Ave., JM-7, Columbus, OH 43201, USA; E-Mail:
| |
Collapse
|
20
|
Vianna PCB, Walter EHM, Dias MEF, Faria JAF, Netto FM, Gigante ML. Effect of addition of CO₂ to raw milk on quality of UHT-treated milk. J Dairy Sci 2012; 95:4256-62. [PMID: 22818439 DOI: 10.3168/jds.2012-5387] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 04/05/2012] [Indexed: 11/19/2022]
Abstract
The objective of this study was to evaluate the effect of addition of CO(2) to raw milk on UHT milk quality during storage. Control milk (without CO(2) addition) and treated milk (with CO(2) addition up to pH 6.2) were stored in bulk tanks at 4°C for 6d. After storage, both samples were UHT processed using indirect heating (140°C for 5s). Samples were aseptically packed in low-density polyethylene pouches and stored in the dark at room temperature. Raw milk was evaluated upon receipt for physicochemical composition, proteolysis, lipolysis, standard plate count, psychrotrophic bacteria, and Pseudomonas spp. counts, and after 6d of storage for proteolysis, lipolysis, and microbial counts. After processing, UHT milk samples were evaluated for physicochemical composition, proteolysis, and lipolysis. Samples were evaluated for proteolysis and lipolysis twice a month until 120d. Peptides from pH 4.6-soluble N filtrates were performed by reversed-phase HPLC after 1 and 120d of storage. A split-plot design was used and the complete experiment was carried out in triplicate. The results were evaluated by ANOVA and Tukey's test. After 6d of storage, CO(2)-treated raw milk kept its physicochemical and microbiological quality, whereas the untreated milk showed significant quality losses. A significant increase in proteolysis occurred during 120d of storage in both treatments, but the increase occurred 1.4 times faster in untreated UHT milk than in CO(2)-treated UHT milk. In both UHT milks, the proteolysis was a consequence of the action of plasmin and microbial proteases. However, the untreated UHT milk showed higher microbial protease activity than the treated UHT milk. The addition of CO(2) to the raw milk maintained the quality during storage, resulting in UHT milk with less proteolysis and possibly longer shelf life, which is usually limited by age gelation of UHT milk.
Collapse
Affiliation(s)
- P C B Vianna
- Universidade Norte do Paraná Mestrado em Ciência e Tecnologia do leite Avenida Paris n. 675, CEP 86041-140, Londrina/PR, Brazil.
| | | | | | | | | | | |
Collapse
|
21
|
Dagostin JLA, Carpine D, Masson ML. Influence of Acidification Method on Composition, Texture, Psychrotrophs, and Lactic Acid Bacteria in Minas Frescal Cheese. FOOD BIOPROCESS TECH 2012. [DOI: 10.1007/s11947-012-1029-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
22
|
SINGH PREETI, WANI ALIABAS, KARIM AA, LANGOWSKI HORSTCHRISTIAN. The use of carbon dioxide in the processing and packaging of milk and dairy products: A review. INT J DAIRY TECHNOL 2011. [DOI: 10.1111/j.1471-0307.2011.00744.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
23
|
Abstract
This work aimed to assess the growth and survival of four foodborne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus) in beer. The effects of ethanol, pH, and storage temperature were investigated for the gram-negative pathogens (E. coli O157:H7 and Salmonella Typhimurium), whereas the presence of hops ensured that the gram-positive pathogens (L. monocytogenes and S. aureus) were rapidly inactivated in alcohol-free beer. The pathogens E. coli O157:H7 and Salmonella Typhimurium could not grow in the mid-strength or full-strength beers, although they could survive for more than 30 days in the mid-strength beer when held at 4°C. These pathogens grew rapidly in the alcohol-free beer; however, growth was prevented when the pH of the alcohol-free beer was lowered from the "as received" value of 4.3 to 4.0. Pathogen survival in all beers was prolonged at lowered storage temperatures.
Collapse
Affiliation(s)
- Garry Menz
- Institute of Food & Crop Science, School of Science & Engineering, University of Ballarat, Ballarat, Australia
| | | | | |
Collapse
|
24
|
Dachet F, St-Gelais D, Roy D, LaPointe G. Transcriptome profiling of lactococcal mixed culture activity in milk by fluorescent RNA arbitrarily primed-PCR. ACTA ACUST UNITED AC 2010. [DOI: 10.1051/dst/2010020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
|
25
|
Rasolofo EA, St-Gelais D, LaPointe G, Roy D. Molecular analysis of bacterial population structure and dynamics during cold storage of untreated and treated milk. Int J Food Microbiol 2010; 138:108-18. [DOI: 10.1016/j.ijfoodmicro.2010.01.008] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Revised: 01/09/2010] [Accepted: 01/12/2010] [Indexed: 10/19/2022]
|
26
|
Jackson DN, Davis B, Tirado SM, Duggal M, van Frankenhuyzen JK, Deaville D, Wijesinghe MAK, Tessaro M, Trevors JT. Survival mechanisms and culturability of Campylobacter jejuni under stress conditions. Antonie van Leeuwenhoek 2009; 96:377-94. [PMID: 19774483 DOI: 10.1007/s10482-009-9378-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Accepted: 09/03/2009] [Indexed: 11/24/2022]
Abstract
Culture-based isolation and enumeration of bacterial human pathogens from environmental and human food samples has significant limitations.Many pathogens enter a viable but non-culturable(VBNC) state in response to stress, and cannot be detected via culturing methods. Favourable growth conditions with a source of energy and an ideal stoichiometric ratio of carbon to inorganic elements can reverse this VBNC state. This review will focus on the bacterium Campylobacter jejuni which is a leading cause of food borne illness in the developed world. C. jejuni can enter a VBNC state in response to extremes in: pH, moisture content, temperature,nutrient content and salinity. Once in a VBNC state,the organism must maintain an energy balance from substrate oxidation through respiration to grow,divide and remain viable. The goal of this review isa greater understanding of how abiotic stress and thermodynamics influence the viability of C. jejuni.
Collapse
Affiliation(s)
- D Nathan Jackson
- School of Environmental Sciences, University of Guelph, Guelph, ON N1G2Wl, Canada
| | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Hotchkiss JH, Werner BG, Lee EY. Addition of Carbon Dioxide to Dairy Products to Improve Quality: A Comprehensive Review. Compr Rev Food Sci Food Saf 2006. [DOI: 10.1111/j.1541-4337.2006.00008.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
28
|
Werner BG, Hotchkiss JH. Continuous Flow Nonthermal CO2 Processing: The Lethal Effects of Subcritical and Supercritical CO2 on Total Microbial Populations and Bacterial Spores in Raw Milk. J Dairy Sci 2006; 89:872-81. [PMID: 16507680 DOI: 10.3168/jds.s0022-0302(06)72151-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The effect of pressurized (<50 MPa) CO2 as a nonthermal process for bacterial reduction in raw skim milk was examined using a unique pressurized continuous flow system. The lethal effects of subcritical and super-critical CO2 applied at different temperatures and pressures toward total native psychrotrophic microbial populations, total inoculated Pseudomonas fluorescens, and total inoculated spore populations were studied and compared. Pressures between 10.3 and 48.3 MPa; temperatures of 15, 30, 35, and 40 degrees C; and CO2 concentrations of 0, 3, 66, and 132 g/kg of milk were studied. For both native populations and inoculated P. fluorescens, greater total microbial lethality was observed under supercritical CO2 conditions than under subcritical CO2 conditions. At 30 degrees C, there was no effect on total microbial lethality of increasing pressure up to 20.7 MPa with either 66 or 132 g/kg of CO2; at 35 degrees C, there was a positive relationship between pressure and lethality at CO2 levels of 132 g/kg, but no relationship at 66 g/kg of CO2. For total microbial populations and P. fluorescens, CO2 applied at 132 g/kg at 30 degrees C and pressures of 10.3 to 20.7 MPa resulted in an average standard plate count reduction of 3.81 and 2.93 log, respectively; at 35 degrees C and 20.7 MPa, maximum reductions achieved were 5.36 and 5.02 log, respectively. For both total microbial populations and inoculated P. fluorescens, CO2 exhibited a greater overall lethal effect at 132 g/kg than at 66 g/kg and a greater effect at 35 degrees C than at 30 degrees C. At 24.1 and 48.3 MPa and 40 degrees C, microbial lethality in raw aged milk treated with 3 g/kg of CO2 was not significantly different than that observed for uncarbonated milk; lethality achieved in milk treated with 132 g/kg of CO2 was significantly higher than that achieved in these 2 low-level CO2 treatments. No treatment studied had any significant impact on spore populations. Our work shows that, using the studied system, pressurized CO2 results in greater microbial lethality in milk above critical temperatures than below and suggests that a critical concentration threshold level of CO2 is required for lethal effects. Our work also suggests that supercritical CO2 processing in a continuous flow system can achieve reductions in some microbial populations equal to or better than that typically achieved during high-temperature, short-time pasteurization.
Collapse
Affiliation(s)
- B G Werner
- Department of Food Science, Cornell University, Ithaca, NY 14853, USA
| | | |
Collapse
|
29
|
Lee KJ, Bae SM, Lee MR, Yeon SM, Lee YH, Kim KS. Proteomic analysis of growth phase-dependent proteins ofStreptococcus pneumoniae. Proteomics 2006; 6:1274-82. [PMID: 16429463 DOI: 10.1002/pmic.200500415] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Streptococcus pneumoniae is an important human pathogen that causes a variety of diseases, such as pneumonia, bacteremia, meningitis, otitis media, and sinusitis, in both adults and children. The global pattern of growth phase-dependent protein expression of S. pneumoniae during in vitro culture was analyzed using 2-DE combined with MALDI-TOF MS and LC/ESI-MS/MS. Several protein production patterns were observed at four time points throughout the growth stage, although some protein levels did not change significantly. We focused on the switch in protein expression at the transition from log growth phase to stationary phase. Proteins that were significantly induced or repressed at this point are likely to be involved in central intermediary metabolism, amino acid synthesis, nucleotide, and fatty acid metabolism, cell wall synthesis, protein degradation, and stress responses. This global expression profiling approach has revealed previously unrecognized relationships between proteins in the life of this pathogen.
Collapse
Affiliation(s)
- Kwang-Jun Lee
- Division of Bacterial Respiratory Infections, Department of Microbiology, National Institute of Health, Korea Center for Diseases Control and Prevention, Eunpyung-Ku, Seoul, Korea
| | | | | | | | | | | |
Collapse
|
30
|
Chang SW, Shieh CJ, Lee GC, Akoh CC, Shaw JF. Optimized Growth Kinetics of Pichia pastoris and Recombinant Candida rugosa LIP1 Production by RSM. J Mol Microbiol Biotechnol 2006; 11:28-40. [PMID: 16825788 DOI: 10.1159/000092817] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
A predictive model for Pichia pastoris expression of highly active recombinant Candida rugosa LIP1 was developed by combining the Gompertz function and response surface methodology (RSM) to evaluate the effect of yeast extract concentration, glucose concentration, temperature, and pH on specific responses. Each of the responses (maximum population densities, specific growth rate (mumax), protein concentration, and minimum lag phase duration) was determined using the modified Gompertz function. RSM and 4-factor-5-level central composite rotatable design (CCRD) were adopted to evaluate the effects of growth parameters, such as temperature (21.6-38.4 degrees C), glucose concentration (0.3-3.7%), yeast extract (0.16-1.84%), and pH (5.3-8.7) on the responses of P. pastoris growth kinetics. Based on ridge maximum analysis, the optimum population density conditions were: temperature 24.4 degrees C, glucose concentration 2.0%, yeast extract 1.5%, and pH 7.6. The optimum specific growth rate conditions were: temperature 28.9 degrees C, glucose concentration 2.0%, yeast extract 1.1%, and pH 6.9. The optimum protein concentration conditions were: temperature 24.2 degrees C, glucose concentration 1.9%, yeast extract 1.5%, and pH 7.6. Based on ridge minimum analysis, the minimal lag phase conditions were: temperature 32.3 degrees C, glucose concentration 2.1%, yeast extract 1.1%, and pH 5.4. For the predicted value, the maximum population density, specific growth rate, protein concentration, and minimum lag phase duration were 15.7 mg/ml, 3.4 h(-1), 0.78 mg/ml, and 4.2 h, and the actual values were 14.3 +/- 3.5 mg/ml, 3.6 +/- 0.6 h(-1), 0.72 +/- 0.2 mg/ml, and 4.4 +/- 1.6 h, respectively.
Collapse
Affiliation(s)
- Shu-Wei Chang
- Institute of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan
| | | | | | | | | |
Collapse
|
31
|
Abstract
The effects of holding raw milk under carbon dioxide pressures of 68 to 689 kPa at temperatures of 5, 6.1, 10, and 20 degrees C on the indigenous microbiota were investigated. These pressure-temperature combinations did not cause precipitation of proteins from the milk. Standard plate counts from treated milks demonstrated significantly lower growth rate compared with untreated controls at all temperatures, and in some cases, the treatment was microcidal. Raw milk treated with CO2 and held at 6.1 degrees C for 4 d exhibited reduced bacterial growth rates at pressures of 68, 172, 344, and 516 kPa; and at 689 kPa, demonstrated a significant loss of viability in standard plate count assays. The 689-kPa treatment also reduced gram-negative bacteria and total Lactobacillus spp. The time required for raw milk treated at 689 kPa and held at 4 degrees C to reach 4.30 log10 cfu/mL increased by 4 d compared with untreated controls. Total coliform counts in the treated milk were maintained at 1.95 log10 cfu/mL by d 9 of treatment, whereas counts in the control significantly increased to 2.61 log10 cfu/mL by d 4 and 2.89 log10 cfu/mL by d 9. At d 8, Escherichia coli counts had not significantly changed in treated milk, but significantly increased in the control milk. Thermoduric bacteria counts after 8 d were 1.32 log10 cfu/mL in treated milk and 1.98 log10 cfu/mL in control milk. These data indicated that holding raw milk at low CO2 pressure reduces bacterial growth rates without causing milk protein precipitation. Combining low CO2 pressure and refrigeration would improve the microbiological quality and safety of raw milk and may be an effective strategy for shipping raw single strength or concentrated milk over long distances.
Collapse
Affiliation(s)
- M Rajagopal
- Department of Food Science, Cornell University, Ithaca, NY 14853, USA
| | | | | |
Collapse
|