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Louis D, Florence P, Ivan L, Anne-Gabrielle M. Detection of risk areas in dairy powder processes: The development of thermophilic spore forming bacteria taking into account their growth limits. Int J Food Microbiol 2024; 418:110716. [PMID: 38669747 DOI: 10.1016/j.ijfoodmicro.2024.110716] [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: 10/25/2023] [Revised: 04/16/2024] [Accepted: 04/21/2024] [Indexed: 04/28/2024]
Abstract
Anoxybacillus flavithermus, Geobacillus stearothermophilus and Bacillus licheniformis are the main contaminants found in dairy powders. These spore-forming thermophilic bacteria, rarely detected in raw milk, persist, and grow during the milk powder manufacturing process. Moreover, in the form of spores, these species resist and concentrate in the powders during the processes. The aim of this study was to determine the stages of the dairy powder manufacturing processes that are favorable to the growth of such contaminants. A total of 5 strains were selected for each species as a natural contaminant of dairy pipelines in order to determine the minimum and maximum growth enabling values for temperature, pH, and aw and their optimum growth rates in milk. These growth limits were combined with the environmental conditions of temperature, pH and aw encountered at each step of the manufacture of whole milk, skim milk and milk protein concentrate powders to estimate growth capacities using cardinal models and the Gamma concept. These simulations were used to theoretically calculate the population sizes reached for the different strains studied at each stage in between two successive cleaning in place procedures. This approach highlights the stages at which risk occurs for the development of spore-forming thermophilic bacterial species. During the first stages of production, i.e. pre-treatment, pasteurization, standardization and pre-heating before concentration, physico-chemical conditions encountered are suitable for the development and growth of A. flavithermus, G. stearothermophilus and B. licheniformis. During the pre-heating stage and during the first effects in the evaporators, the temperature conditions appear to be the most favorable for the growth of G. stearothermophilus. The temperatures in the evaporator during the last evaporator effects are favorable for the growth of B. licheniformis. In the evaporation stage, low water activity severely limits the development of A. flavithermus.
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Affiliation(s)
- Delaunay Louis
- Univ Brest, INRAE, Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, 29000 Quimper, France
| | - Postollec Florence
- ADRIA Food Technology Institute, UMT ACTIA 19.03 ALTER'iX, Z.A. de Creac'h Gwen, 29196, Quimper, Cedex, France
| | - Leguerinel Ivan
- Univ Brest, INRAE, Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, 29000 Quimper, France.
| | - Mathot Anne-Gabrielle
- Univ Brest, INRAE, Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, 29000 Quimper, France
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2
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Hongchao D, Ma L, Xu Z, Soteyome T, Yuan L, Yang Z, Jiao XA. Invited review: Role of Bacillus licheniformis in the dairy industry- friends or foes? J Dairy Sci 2024:S0022-0302(24)00904-4. [PMID: 38851582 DOI: 10.3168/jds.2024-24826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2024] [Accepted: 05/07/2024] [Indexed: 06/10/2024]
Abstract
Bacillus licheniformis is one of the major spore-forming bacteria with great genotypic diversity in raw milk, dairy ingredients, final dairy products, and is found throughout the dairy processing continuum. Though being widely used as a probiotic strain, this species also serves as a potential risk in the dairy industry based on its roles in foodborne illness and dairy spoilage. Biofilm formation of B. licheniformis in combined with the heat resistance of its spores, make it impossible to prevent the presence of B. licheniformis in final dairy products by traditional cleaning and disinfection procedures. Despite the extensive efforts on the identification of B. licheniformis from various dairy samples, no reviews have been reported on both hazard and benefits of this spore-former. This review discusses the prevalence of B. licheniformis from raw milk to commercial dairy products, biofilm formation and spoilage potential of B. licheniformis, and its potential prevention methods. In addition, the potential benefits of B. licheniformis in the dairy industry were also summarized.
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Affiliation(s)
- Dai Hongchao
- School of Food Science and Engineering, Yangzhou University, Yangzhou, Jiangsu, 225127 China; Jiangsu Key Laboratory of Zoonoses, Yangzhou, Jiangsu, 225009 China
| | - Lili Ma
- School of Food Science and Engineering, Yangzhou University, Yangzhou, Jiangsu, 225127 China
| | - Zhenbo Xu
- School of Food Science and Engineering, Guangdong Province Key Laboratory for Green Processing of Natural Products and Product Safety, Engineering Research Center of Starch and Vegetable Protein Processing Ministry of Education, South China University of Technology, Guangzhou 510640, China; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Home Economics Technology, Rajamangala University of Technology Phra Nakhon, Bangkok, Thailand
| | - Thanapop Soteyome
- Home Economics Technology, Rajamangala University of Technology Phra Nakhon, Bangkok, Thailand
| | - Lei Yuan
- School of Food Science and Engineering, Yangzhou University, Yangzhou, Jiangsu, 225127 China; Jiangsu Key Laboratory of Zoonoses, Yangzhou, Jiangsu, 225009 China.
| | - Zhenquan Yang
- School of Food Science and Engineering, Yangzhou University, Yangzhou, Jiangsu, 225127 China
| | - Xin-An Jiao
- Jiangsu Key Laboratory of Zoonoses, Yangzhou, Jiangsu, 225009 China
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Park SM, Rhee MS. Prevalence and phylogenetic traits of nitrite-producing bacteria in raw ingredients and processed baby foods: Potential sources of foodborne infant methemoglobinemia. Food Res Int 2024; 178:113966. [PMID: 38309914 DOI: 10.1016/j.foodres.2024.113966] [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: 08/05/2023] [Revised: 12/19/2023] [Accepted: 01/02/2024] [Indexed: 02/05/2024]
Abstract
Nitrite, which has been mainly regarded as a chemical hazard, can induce infant methemoglobinemia. As for nitrite as a product of microbial metabolism, the contribution of the oral or gut microbiome has mostly received attention, whereas the role of nitrite-producing bacteria (NPBs) in food has been less elucidated. In this study, mesophilic NPBs were isolated from food samples (n = 320) composed of raw ingredients for weaning foods (n = 160; beetroot, broccoli, carrot, lettuce, rice powder, spinach, sweet potato, and honey) and processed baby foods (n = 160; cereal snack, cheese, yogurt, powdered infant formula, sorghum syrup, vegetable fruit juice, and weaning food). The phylogenetic diversity of the NPB strains was analyzed via 16S rRNA sequencing. All 15 food items harbored NPBs, with a prevalence of 71.9 % and 34.4 % for the raw ingredients and processed foods, respectively. The NPBs isolated from the foods were identified as Actinomycetota (Actinomycetes), Bacteroidota (Flavobacteriia, Sphingobacteriia), Bacillota (Bacilli), or Pseudomonadota (Alpha-, Beta-, and Gammaproteobacteria). Among the raw and processed foods, beetroot (85.0 %) and powdered infant formula (70.0 %) showed had the highest NPB prevalence (P > 0.05). Bacillota predominated in both types of food. The contamination source of Pseudomonadota, which was another major phylum present in the raw ingredients, was presumed to be the soil and endophytes in the seeds, whereas that of Bacillota was the manufacturing equipment used with the raw ingredients. Common species for probiotics, such as Lacticaseibacillus, Leuconostoc, Enterococcus, and Bacillus, were isolated and identified as NPBs. To our knowledge, this is the first study to reveal the taxonomical diversity and omnipresence of NPBs in food for babies. The results of this study highlight the importance of food-mediated microbiological risks of infant methemoglobinemia which are yet underrecognized.
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Affiliation(s)
- Sun Min Park
- Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Min Suk Rhee
- Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea.
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4
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Abele M, Doll E, Bayer FP, Meng C, Lomp N, Neuhaus K, Scherer S, Kuster B, Ludwig C. Unified Workflow for the Rapid and In-Depth Characterization of Bacterial Proteomes. Mol Cell Proteomics 2023; 22:100612. [PMID: 37391045 PMCID: PMC10407251 DOI: 10.1016/j.mcpro.2023.100612] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 05/18/2023] [Accepted: 06/26/2023] [Indexed: 07/02/2023] Open
Abstract
Bacteria are the most abundant and diverse organisms among the kingdoms of life. Due to this excessive variance, finding a unified, comprehensive, and safe workflow for quantitative bacterial proteomics is challenging. In this study, we have systematically evaluated and optimized sample preparation, mass spectrometric data acquisition, and data analysis strategies in bacterial proteomics. We investigated workflow performances on six representative species with highly different physiologic properties to mimic bacterial diversity. The best sample preparation strategy was a cell lysis protocol in 100% trifluoroacetic acid followed by an in-solution digest. Peptides were separated on a 30-min linear microflow liquid chromatography gradient and analyzed in data-independent acquisition mode. Data analysis was performed with DIA-NN using a predicted spectral library. Performance was evaluated according to the number of identified proteins, quantitative precision, throughput, costs, and biological safety. With this rapid workflow, over 40% of all encoded genes were detected per bacterial species. We demonstrated the general applicability of our workflow on a set of 23 taxonomically and physiologically diverse bacterial species. We could confidently identify over 45,000 proteins in the combined dataset, of which 30,000 have not been experimentally validated before. Our work thereby provides a valuable resource for the microbial scientific community. Finally, we grew Escherichia coli and Bacillus cereus in replicates under 12 different cultivation conditions to demonstrate the high-throughput suitability of the workflow. The proteomic workflow we present in this manuscript does not require any specialized equipment or commercial software and can be easily applied by other laboratories to support and accelerate the proteomic exploration of the bacterial kingdom.
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Affiliation(s)
- Miriam Abele
- Bavarian Center for Biomolecular Mass Spectrometry (BayBioMS), TUM School of Life Sciences, Technical University of Munich, Freising, Germany; Division of Proteomics and Bioanalytics, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Etienne Doll
- Division of Microbial Ecology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Florian P Bayer
- Division of Proteomics and Bioanalytics, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Chen Meng
- Bavarian Center for Biomolecular Mass Spectrometry (BayBioMS), TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Nina Lomp
- Bavarian Center for Biomolecular Mass Spectrometry (BayBioMS), TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Klaus Neuhaus
- Division of Microbial Ecology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany; Core Facility Microbiome, ZIEL - Institute for Food & Health, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Siegfried Scherer
- Division of Microbial Ecology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Bernhard Kuster
- Bavarian Center for Biomolecular Mass Spectrometry (BayBioMS), TUM School of Life Sciences, Technical University of Munich, Freising, Germany; Division of Proteomics and Bioanalytics, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Christina Ludwig
- Bavarian Center for Biomolecular Mass Spectrometry (BayBioMS), TUM School of Life Sciences, Technical University of Munich, Freising, Germany.
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Malek F. Flow of spore-forming bacteria between suppliers of dairy powders and users in some developing countries: challenges and perspectives. JOURNAL OF FOOD SCIENCE AND TECHNOLOGY 2023; 60:2132-2142. [PMID: 37273561 PMCID: PMC10232714 DOI: 10.1007/s13197-022-05495-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Revised: 04/07/2022] [Accepted: 05/19/2022] [Indexed: 06/06/2023]
Abstract
Abstract Spore-forming bacteria are common contaminants of milk powder and processing lines and a major concern for the dairy industry. This dairy-associated microflora was studied extensively and well characterized in developed countries (exporters of milk powder), compared to developing countries (importers). Thereby, the quality issues affecting dairy powders and derived products are not fully controlled in developing countries. That is the case in Algeria, where recombined or reconstituted pasteurized milk is of low quality, reduced shelf-life, and the related dairies faced recurrent contaminations due to spores and biofilms. The transfer of spore-forming bacteria from exporters of dairy powders to importers in developing countries is an interesting topic, not thoroughly investigated. In addition, milk powder-based products are growing worldwide and their attributes, processes and technologies need to be better understood and controlled. This review analyzes issues affecting milk powder quality, based on few studies from developing countries in comparison with current knowledge, and emphasis on the case in Algeria. It provides information on how spore-forming bacteria and their biofilms affect the quality and shelf-life of recombined pasteurized milk produced in Algeria and compromise hygiene conditions in local dairy plants. Challenges and perspectives for better management of spore transfer from exporters of dairy powders to importers in developing countries are thereby outlined. Highlights The presence of spore-forming bacteria in milk powder is a serious safety issue.Spores are not well known, characterized and controlled in importers from developing countries.Spores cause recurrent contamination of pasteurized milk and biofilm issues in Algerian dairies.Challenges are how to reduce the flow of spores in milk powder trade.Perspectives on identification targeting predominant spores and improvement of biofilm removal.
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Affiliation(s)
- Fadila Malek
- Department of Biology, Faculty SNV-STU, University of Tlemcen, 13000 Tlemcen, Algeria
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6
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Zhang Y, Wu Q, Forsythe S, Liu C, Chen N, Li Y, Zhang J, Wang J, Ding Y. The cascade regulation of small RNA and quorum sensing system: Focusing on biofilm formation of foodborne pathogens in food industry. FOOD BIOSCI 2023. [DOI: 10.1016/j.fbio.2023.102472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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7
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Yuan L, Fan L, Liu S, Sant'Ana AS, Zhang Y, Zhou W, Zheng X, He G, Yang Z, Jiao X. Bacterial community analysis of infant foods obtained from Chinese markets by combining culture-dependent and high-throughput sequence methods. Food Res Int 2022; 162:112060. [DOI: 10.1016/j.foodres.2022.112060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 09/23/2022] [Accepted: 10/07/2022] [Indexed: 11/04/2022]
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Li H, Zhang Y, Yuan X, Liu S, Fan L, Zheng X, Wang S, Yuan L, Jiao X. Microbial biodiversity of raw milk collected from Yangzhou and the heterogeneous biofilm‐forming ability of
Pseudomonas. INT J DAIRY TECHNOL 2022. [DOI: 10.1111/1471-0307.12905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Huaxiang Li
- College of Food Science and Engineering Yangzhou University Yangzhou Jiangsu 225127 China
| | - Yanhe Zhang
- College of Food Science and Engineering Yangzhou University Yangzhou Jiangsu 225127 China
| | - Xinhai Yuan
- College of Food Science and Engineering Yangzhou University Yangzhou Jiangsu 225127 China
| | - Siqi Liu
- College of Food Science and Engineering Yangzhou University Yangzhou Jiangsu 225127 China
| | - Luyao Fan
- College of Food Science and Engineering Yangzhou University Yangzhou Jiangsu 225127 China
| | - Xiangfeng Zheng
- College of Food Science and Engineering Yangzhou University Yangzhou Jiangsu 225127 China
| | - Shuo Wang
- College of Food Science and Engineering Yangzhou University Yangzhou Jiangsu 225127 China
| | - Lei Yuan
- College of Food Science and Engineering Yangzhou University Yangzhou Jiangsu 225127 China
| | - Xinan Jiao
- Jiangsu Key Laboratory of Zoonoses Yangzhou Jiangsu 225009 China
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9
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Wedel C, Atamer Z, Dettling A, Wenning M, Scherer S, Hinrichs J. Towards low-spore milk powders: A review on microbiological challenges of dairy powder production with focus on aerobic mesophilic and thermophilic spores. Int Dairy J 2022. [DOI: 10.1016/j.idairyj.2021.105252] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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10
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Dynamic tracing of bacterial community distribution and biofilm control of dominant species in milk powder processing. Lebensm Wiss Technol 2022. [DOI: 10.1016/j.lwt.2021.112855] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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11
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Wang N, Jin Y, He G, Yuan L. Development of multi-species biofilm formed by thermophilic bacteria on stainless steel immerged in skimmed milk. Food Res Int 2021; 150:110754. [PMID: 34865772 DOI: 10.1016/j.foodres.2021.110754] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/22/2021] [Accepted: 10/10/2021] [Indexed: 11/26/2022]
Abstract
Thermophilic bacteria, such as Bacillus licheniformis, Geobacillus stearothermophilus, Bacillus Subtilis and Anoxybacillus flavithermus, are detected frequently in milk powder products. Biofilms of those strains act as a major contamination to milk powder manufactures and pose potential risks in food safety. In this study, we explored the developing process of multi-species biofilm formed by the four thermophilic bacteria on stainless steel immerged in skimmed milk. The results showed that the thermophilic strains possessed strong capacities to decompose proteins and lactose in skimmed milk, and the spoilage effects were superimposed from multiple strains. B. licheniformis was the most predominant species in the mixed-species biofilm after 12-h incubation. From 24 h to 48 h, G. stearothermophilus occupied the highest proportion. Within the multi-species biofilm, competitive relation existed between B. licheniformis and G. stearothermophilus, while synergistic impacts were observed between B. licheniformis and A. flavithermus. The interspecies mutual influences on biofilm development provided important evidences for understanding colonization of the predominant thermophilic bacteria during milk powder processing.
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Affiliation(s)
- Ni Wang
- School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
| | - Yujie Jin
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - Guoqing He
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China.
| | - Lei Yuan
- College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, China.
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Alonso VPP, de Oliveira Morais J, Kabuki DY. Incidence of Bacillus cereus, Bacillus sporothermodurans and Geobacillus stearothermophilus in ultra-high temperature milk and biofilm formation capacity of isolates. Int J Food Microbiol 2021; 354:109318. [PMID: 34246014 DOI: 10.1016/j.ijfoodmicro.2021.109318] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 06/02/2021] [Accepted: 06/19/2021] [Indexed: 12/19/2022]
Abstract
The presence of mesophilic and thermophilic spore-forming bacteria in UHT milk, as well as biofilm formation in dairy plants, are concerning. The current study explored the spore-forming bacilli diversity in 100 samples of UHT milk (skimmed and whole). Through this work, a total of 239 isolates from UHT milk samples were obtained. B. cereus s.s. was isolated from 7 samples, B. sporothermodurans from 19 and, G. stearothermophilus from 25 samples. Genes encoding hemolysin (HBL), and non-hemolytic (NHE) enterotoxins were detected in B. cereus s.s. isolates. All isolates of B. cereus s.s. (12) B. sporothermodurans (38), and G. stearothermophilus (47) were selected to verify the ability of biofilm formation in microtiter plates. The results showed all isolates could form biofilms. The OD595 values of biofilm formation varied between 0.14 and 1.04 for B. cereus, 0.20 to 1.87 for B. sporothermodurans, and 0.49 to 2.77 for G. stearothermophilus. The data highlights that the dairy industry needs to reinforce control in the initial quality of the raw material and in CIP cleaning procedures; avoiding biofilm formation and consequently a persistent microbiota in processing plants, which can shelter pathogenic species such as B. cereus s.s.
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Affiliation(s)
- Vanessa Pereira Perez Alonso
- Department of Food Science and Nutrition, School of Food Engineering, State University of Campinas, Campinas, SP, Brazil.
| | - Jéssica de Oliveira Morais
- Department of Food Science and Nutrition, School of Food Engineering, State University of Campinas, Campinas, SP, Brazil
| | - Dirce Yorika Kabuki
- Department of Food Science and Nutrition, School of Food Engineering, State University of Campinas, Campinas, SP, Brazil
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Abstract
The dairy industry produces large amounts of wastewater, including white and cleaning wastewater originating principally from rinsing and cleaning-in-place procedures. Their valorization into process water and non-fat milk solids, in the case of white wastewater, or the renewal of cleaning solutions could be achieved using pressure-driven membrane processes. However, it is crucial to determine the intrinsic characteristics of wastewaters, such as proximate composition and bacterial composition, to optimize their potential for valorization. Consequently, white and cleaning wastewaters were sampled from industrial-scale pasteurizers located in two different Canadian dairy processing plants. Bacterial profiles of dairy wastewaters were compared to those of tap waters, pasteurized skim milk and unused cleaning solutions. The results showed that the physicochemical characteristics as well as non-fat milk solids contents differed drastically between the two dairy plants due to different processing conditions. A molecular approach combining quantitative real-time polymerase chain reaction (qPCR) and metabarcoding was used to characterize the bacteria present in these solutions. The cleaning solutions did not contain sufficient genomic DNA for sequencing. In white wastewater, the bacterial contamination differed depending on the dairy plant (6.91 and 7.21 log10 16S gene copies/mL). Psychrotrophic Psychrobacter genus (50%) dominated white wastewater from plant A, whereas thermophilic Anoxybacillus genus (56%) was predominant in plant B wastewater. The use of cold or warm temperatures during the pasteurizer rinsing step in each dairy plant might explain this difference. The detailed characterization of dairy wastewaters described in this study is important for the dairy sector to clearly identify the challenges in implementing strategies for wastewater valorization.
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Taxonomic Evaluation of the Heyndrickxia (Basonym Bacillus) sporothermodurans Group ( H. sporothermodurans, H. vini, H. oleronia) Based on Whole Genome Sequences. Microorganisms 2021; 9:microorganisms9020246. [PMID: 33530338 PMCID: PMC7911792 DOI: 10.3390/microorganisms9020246] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/21/2021] [Accepted: 01/24/2021] [Indexed: 11/17/2022] Open
Abstract
The genetic heterogeneity of Heyndrickxia sporothermodurans (formerly Bacillussporothermodurans) was evaluated using whole genome sequencing. The genomes of 29 previously identified Heyndrickxiasporothermodurans and two Heyndrickxia vini strains isolated from ultra-high-temperature (UHT)-treated milk were sequenced by short-read (Illumina) sequencing. After sequence analysis, the two H. vini strains could be reclassified as H. sporothermodurans. In addition, the genomes of the H.sporothermodurans type strain (DSM 10599T) and the closest phylogenetic neighbors Heyndrickxiaoleronia (DSM 9356T) and Heyndrickxia vini (JCM 19841T) were also sequenced using both long (MinION) and short-read (Illumina) sequencing. By hybrid sequence assembly, the genome of the H. sporothermodurans type strain was enlarged by 15% relative to the short-read assembly. This noticeable increase was probably due to numerous mobile elements in the genome that are presumptively related to spore heat tolerance. Phylogenetic studies based on 16S rDNA gene sequence, core genome, single-nucleotide polymorphisms and ANI/dDDH, showed that H. vini is highly related to H. sporothermodurans. When examining the genome sequences of all H.sporothermodurans strains from this study, together with 4 H. sporothermodurans genomes available in the GenBank database, the majority of the 36 strains examined occurred in a clonal lineage with less than 100 SNPs. These data substantiate previous reports on the existence and spread of a genetically highly homogenous and heat resistant spore clone, i.e., the HRS-clone.
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