Differences in Carbohydrates Utilization and Antibiotic Resistance Between Streptococcus macedonicus and Streptococcus thermophilus Strains Isolated from Dairy Products in Italy

Abstract

Streptococcus thermophilus and S. macedonicus are the only two species of the genus related to food productions so far known. In the present study, eight S. thermophilus and seven S. macedonicus strains isolated from dairy environments in Italy were compared in order to evidence possible species-specific technological characteristics. Their capability to use lactose, galactose, fructose, and glucose, sugars commonly present in foods and two carbohydrates considered as prebiotics, xylose and inulin, along with the respective growth kinetics were studied. Results showed a luxuriant growth on lactose and different behaviors on galactose, glucose, and fructose. No growth on inulin and xylose was recorded, which is a positive feature for strains intended to be used as starter cultures. Growth parameters, namely, λ, µ, and N, were estimated by using the Gompertz model. Antibiotic resistance to 14 drugs revealed an overall similar behavior between the two species with only a marked difference regarding gentamycin. Antimicrobial activity was also tested against six deleterious bacterial strains, but none of the strains evidenced inhibitory capabilities. The results presented here could be helpful to compare technological potentialities of the two species and to choose strains of the most suitable species for selected microbiological food transformations.

Genomic and phenotypic analyses of exopolysaccharide biosynthesis in Streptococcus thermophilus S-3

“…A higher concentration (4%) of galactose also reduced cell growth. The results are similar to those for S. thermophilus strains isolated from dairy products in Italy by Tarrah et al (2018). Most, S. thermophilus strains prefer lactose to galactose or glucose as a major carbon and energy source (Anbukkarasi et al, 2014) because they have a galactose-negative (Gal − ) phenotype that cannot metabolize galactose.…”

Streptococcus thermophilus ST285 Alters Pro-Inflammatory to Anti-Inflammatory Cytokine Secretion against Multiple Sclerosis Peptide in Mice

“…The Streptococcus genus constitutes over 100 species, amongst which S. thermophilus (ST) are non-pathogenic and food related bacteria that represent outstanding technological features in the food industry [27]. ST are commonly used as secondary starter cultures in dairy products to transform lactose into lactic acid and to acidify the pH of milk [27,28], contributing to both the fermentation and flavoring of dairy products [29]. Most probiotics belong to lactic acid bacteria (LAB); Gram-positive lactic acid producing bacteria that include lactobacilli, bifidobacterial, and enterococci [3].…”

In vitro Probiotic Potential and Anti-cancer Activity of Newly Isolated Folate-Producing Streptococcus thermophilus Strains

“…Regarding the influence of the initial pH of the growth substrate, all strains grew very well at 7.0 while in a medium at pH 6.0 some strains (1F8CT and TH985) were significantly affected and at pH 5.5 all strains grew much slower, although with different kinetics ( Tarrah et al, 2018a ). Regarding the use of different energy sources ( Tarrah et al, 2018c ), all strains were obviously able to use lactose, but only M17PTZA496, MTH17CL396, and TH1436 could use galactose. It has to be considered that galactose accumulation in foods can lead to some unfavorable events, such as cheese fractures due to CO 2 overproduction by heterofermentative bacteria, browning on heat-treated foods such as Mozzarella in pizza preparation, and toxic effects on persons affected by galactosemia, a genetic disease involving galactose metabolism ( Wu et al, 2015 ).…”

“…In particular, the genome of these eight strains had been sequenced and analyzed for the presence of genes related to bacteriocins and production of exopolysaccharides ( Vendramin et al, 2017 ). Moreover, acidification kinetics ( Vendramin et al, 2017 ), growth at different temperatures ( Tarrah et al, 2018b ) and at different pH values ( Tarrah et al, 2018a ), along with the growth dynamics using different energy sources ( Tarrah et al, 2018c ) were evaluated previously. Our work examined the existence of S. thermophilus strains with both good probiotic and technological properties.…”