Ecological Dynamics of Microbiomes in Food Processing Facilities: Pathways to Improved Sanitation

• Author / Creator

  Xu, Zhaohui

• Food processing environments serve as complex niches for bacterial colonization, adaption,
  persistence and dispersal, which subsequently shapes the microbial composition and diversity.
  This Ph.D. dissertation investigated the impact of biofilm formation, bacterial communication and
  cooperation on microbial community assembly, providing insights into the novel and specific
  intervention strategy.
  The presence of microbes in food products depends on contamination from the raw materials or
  microbial communities in food processing facilities. By re-analysing data from 39 published
  studies, we found that while each food commodity possesses its own accessory microbiome, a core
  surface-associated microbiome exists across all commodities. Nutrient levels on food environment
  surfaces significantly impact biofilm community composition more than environmental processing
  surfaces. The longitudinal study in a pork processing facility revealed a high diversity of microbes,
  with addition of 74 novel species. Repeated isolation of the same meat-spoilage-associated strain
  across different sites and times displayed their transmission patterns and persistence over six
  months, pinpointing processing environments as the primary sources of microbes and identified
  specific sites for further interventions.
  The presence of transmissible locus of stress tolerance (tLST) among gamma-proteobacteria
  enhances their microbial resistance to sanitation chemicals in planktonic state cells. Biofilms, the
  natural state of cells in food processing facilities, further reduce sanitation efficacy and facilitate
  microbial dispersal and persistence. Our investigations on the link of tLST to biofilm formation
  and disinfectant resistance showed that the presence of tLST in E. coli yielded higher biofilm
  biomass and enhanced their resistance to chlorine, hydrogen peroxide, and peroxyacetic acid in
  biofilm-embedded cells. The phenotypic switch from floating biofilms (pellicle) to surface-iii
  associated biofilms is regulated more by bacterial communication and cooperation (quorum
  sensing) than unique gene presence/absence.
  The application of ozone nanobubble on meat products in situ and in vitro showed that it displayed
  comparable bactericidal effect to peracetic acid and altered microbial composition, particularly
  eliminating the more undesirable microbes. Taking together, these findings contribute to a better
  understanding of the microbial ecology of food processing environments, facilitate the
  implementation of novel and site-specific interventions and potentially reduce food waste and
  outbreaks, promoting the development of a more sustainable food systems.

• Subjects / Keywords

  • Meat spoilage
  • biofilm
  • microbiome
  • sanitation intervention

• Graduation date

  Fall 2024

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-zn1g-1w98

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.