Pseudomonas spp. and other psychrotrophic microorganisms in inspected and non-inspected Brazilian Minas Frescal cheese: proteolytic, lipolytic and AprX production potential

Abstract

The most consumed cheese in Brazil, Minas Frescal cheese (MFC) is highly susceptible to microbial contamination and clandestine production and commercialization can pose a risk to consumer health. The storage of this fresh product under refrigeration, although more appropriate, may favor the growth of spoilage psychrotrophic bacteria. The objective of this study was to quantify and compare Pseudomonas spp. and other psychrotrophic bacteria in inspected and non-inspected MFC samples, evaluate their lipolytic and proteolytic activities and their metalloprotease production potentials. Twenty MFC samples were evaluated: 10 inspected and 10 non-inspected. Counts of psychrotrophic bacteria and Pseudomonas spp., evaluation of the proteolytic and lipolytic potential of the isolates, and identification of potential producers of alkaline metalloprotease (AprX) were assessed. The mean total psychrotrophic counts were 1.07 (±2.18) × 109CFU/g in the inspected samples and 4.5 (±5.86) × 108CFU/g in the non-inspected, with no significant difference (p=0.37). The average score of Pseudomonas spp. was 6.86 (±18.6) × 105 and 2.08 (±3.65) × 106 CFU/g for the inspected and non-inspected MFC samples, respectively, with no significant difference (p=0.1). Pseudomonas spp. represented 0.06% and 0.004% of psychrotrophic bacteria found in inspected and non-inspected MFC samples, respectively. Collectively, 694 psychrotrophic strains and 47Pseudomonas spp. were isolated, of which 59.9% and 68.1% were simultaneously proteolytic and lipolytic, respectively. Of the 470 psychrotrophs isolated from inspected and 224 from non-inspected cheese samples, 5.74% and 2.23% contained aprX, respectively, while 100 and 86.96% of the Pseudomonas spp. isolates in inspected and non-inspected cheese samples contained the gene. The production potential of AprX did not, however, determine the proteolytic activity on plates of these isolates under the conditions evaluated in this study. Of total, 65.63% of the psychrotrophs that contained aprX gene were confirmed as Pseudomonas spp., using genus-specific PCR. Phylogenetic analysis of the 16S rRNA gene of the other psychrotrophs that were potential producers of AprX identified them as Serratia spp. (n=7), Raoultella ornithinolytica (n=1), and Acinetobacter schindleri (n=1) in the inspected samples and Psychrobacter sanguinis (n=1) and Leuconostoc mesenteroides (n=1) in the non-inspected samples. The production conditions of Brazilian MFC of these samples, while meeting the legal determinations, are not sufficient to control Pseudomonas and other spoilage-related psychrotrophs. Thus, stricter hygienic measures are required during the formal production of this type of cheese.

Bacteria and yeasts associated to Colonial cheese production chain and assessment of their hydrolytic potential

“…The Citrobacter sp., Klebsiella sp. and Raoutella sp., in addition to being opportunistic pathogens, are considered spoilage bacteria (Camargo et al, 2021;Teider Júnior et al, 2019;Jonnala et al, 2018). Although few isolates of gram-negative bacteria were identified, almost all demonstrated having the ability to hydrolyze proteins, lipids, and lactose.…”

“…In Entre Serra and Minas Frescal cheeses, other regional Brazilian cheeses, C. freundii, L. lactis and Kelbsiella sp. were also isolated (Camargo et al, 2021;Teider Júnior et al, 2019).…”

Acompanhamento da microbiota indicadora e patogênica durante a vida útil de Longissimus dorsi (contrafilé) embalado a vácuo

“…One of the major contributors to the decomposition of proteins in food are microorganisms belonging to the Pseudomonas spp. genus, which are known to be psychrotrophic and spoilage agents (Teider et al, 2019;Watson et al, 2023). Considering the significance of these microorganisms in the quality and shelf-life of meat, the psychrotrophs isolated from D-40, prevalence of Pseudomonas spp.…”

Metagenomic of the 16S gene and resistance assessment of "Staphylococcus" spp. isolated from organic and conventional production of Minas Fresch cheese in the state of São Paulo - Brazil

“…In our study, the Pseudomonas genus belonging to this family was the second most prevalent microorganism in the total analysed samples (10.9%). In the literature, several studies have already shown the presence of Pseudomonas in milk and cheeses (Dogan & Boor, 2003;Hammad, 2015;Teider et al, 2019). Bacteria of this genus produce stable lipolytic and proteolytic enzymes after pasteurisation and UHT treatments, thus they can cause deterioration in pasteurised milk during storage under refrigerated conditions.…”

“…For this reason, they are one of the most important agents of deterioration in dairy products (Simões, Simões, & Vieira, 2010). Contamination by this microorganism can occur through the hands of milkers, the surface of the udders, the milking equipment of cows and also through poorly sanitised refrigerated tanks (Teider et al, 2019;Vidal et al, 2017).…”