Shifts of microbiota during cheese production: impact on production and quality.

The high-throughput DNA sequencing (HTS) method is used to identify microbes in cheese and their potential functional properties. The technique can be applied to the microbiota of the cheese processing environment, raw milk, curd, whey, and starter cultures, and be used to improve the quality, safety, and other physicochemical properties of the final product. The HTS method is also utilized to study the microbiota shift of different types of cheeses during processing, as the composition and functional properties of the microbiome provide unique characteristics to different cheeses. Although there are several reviews that focused on microbiota of various types of cheeses, this review focuses on evaluating the microbiota shift of different types of cheese production and highlights key bacteria in each step of the processing as well as microbiota of various types of cheeses. KEY POINTS: • High-throughput sequencing can be applied to identify microbiota in cheese. • Microbiota in cheese is changed during making process and aging. • Starter culture plays an important role to establish microbiota in cheese.

Impact of Operational Parameters on Pathogen Lethality in Dry and Semi-dry Uncooked Fermented Sausages.

The safety of uncooked fermented, dried sausages relies upon controlled fermentation and drying that inactivates pathogenic bacteria. Current guidelines for the production of fermented sausages by the United States Department of Agriculture (USDA) Food Safety Inspection Services (FSIS) and related research highlight specific safety parameters. The confidence that processing steps, which do not include cooking, inherently mitigate microbial risks, is challenged by the resilience of pathogens in the dry and acidic environments of these food products. The aim of this work was to examine the length of drying required to achieve a target pathogen reduction across a range of sausage diameters. This study investigated the relationship between product diameter and time required to achieve target reductions of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes, as well as the attainment of specific water activity (aw). The research utilized salami and summer sausage with diameters of 18 mm, 30 mm, 60 mm, 90 mm, and 110 mm. Sausage batter was inoculated with 5 strains each of E. coli O157:H7, L. monocytogenes, and S. enterica. Inoculated sausages were processed with fermentation and drying protocols for each sausage type. Smaller diameter sausages reached both the desired pathogen reduction and target aw of 0.85 sooner than larger ones. However, the time to achieve the target aw did not align with the time to achieve the pathogen reduction targets, suggesting that aw alone is not a reliable indicator of safety. Another finding was larger sausages achieved the target pathogen reduction without reaching the target aw, suggesting complex relationship between aw, diameter, and pathogen inactivation. These data support the need for food safety guidelines that consider drying duration, aw, and pathogen behavior for varying sausage diameters. This research contributes to developing more precise safety protocols for producing dry and semi-dry fermented sausages.

Multidisciplinary evaluation of plant growth promoting rhizobacteria on soil microbiome and strawberry quality.

The natural soil environment is considered one of the most diverse habitats containing numerous bacteria, fungi, and larger organisms such as nematodes, insects, or rodents. Rhizosphere bacteria play vital roles in plant nutrition and the growth promotion of their host plant. The aim of this study was to evaluate the effects of three plant growth-promoting rhizobacteria (PGPR), Bacillus subtilis, Bacillus amyloliquefaciens, and Pseudomonas monteilii for their potential role as a biofertilizer. The effect of the PGPR was examined at a commercial strawberry farm in Dayton, Oregon. The PGPR were applied to the soil of the strawberry (Fragaria × ananassa cultivar Hood) plants in two different concentrations of PGPR, T1 (0.24% PGPR) and T2 (0.48% PGPR), and C (no PGPR). A total of 450 samples from August 2020 to May 2021 were collected, and microbiome sequencing based on the V4 region of the 16S rRNA gene was conducted. The strawberry quality was measured by sensory evaluation, total acidity (TA), total soluble solids (TSS), color (lightness and chroma), and volatile compounds. Application of the PGPR significantly increased the populations of Bacillus and Pseudomonas and promoted the growth of nitrogen-fixing bacteria. The TSS and color evaluation showed that the PGPR presumptively behaved as a ripening enhancer. The PGPR contributed to the production of fruit-related volatile compounds, while the sensory evaluation did not show significant differences among the three groups. The major finding of this study suggests that the consortium of the three PGPR have a potential role as a biofertilizer by supporting the growth of other microorganisms (nitrogen-fixing bacteria) as part of a synergetic effect and strawberry quality such as sweetness and volatile compounds.

Investigation of soil microbiome under the influence of different mulching treatments in northern highbush blueberry.

Microbial communities on soil are fundamental for the long-term sustainability of agriculture ecosystems. Microbiota in soil would impact the yield and quality of blueberries since microbial communities in soil can interact with the rhizosphere of plant. This study was conducted to determine how different mulching treatments induce changes in soil microbial composition, diversity, and functional properties. A total of 150 soil samples were collected from 5 different mulch treatments (sawdust, green weed mat, sawdust topped with green weed mat, black weed mat, and sawdust topped with black weed mat) at 3 different depths (bottom, middle, and top region of 20 cm soil depth) from 2 different months (June and July 2018). A total of 8,583,839 sequencing reads and 480 operational taxonomic units (OTUs) of bacteria were identified at genus level. Eight different plant growth promoting rhizobacteria (PGPR) were detected, and the relative abundances of Bradyrhizobium, Bacillus, and Paenibacillus were more than 0.1% among all soil samples. Sampling depth and month of soil samples impacted the amount of PGPR, while there were no significant differences based on mulch type. Functional properties of bacteria were identified through PICRUSt2, which found that there is no significant difference between mulch treatment, depth, and month. The results indicated that sampling month and depth of soil impacted the relative abundance of PGPR in soil samples, but there were no significant differences of functional properties and beneficial microbial communities based on mulch type.