A study on the ability of new microbial strains to assimilate biodiesel-derived glycerol at low purity (75%
/
) and produce extra-cellular platform chemical compounds of major interest was carried ...out. After screening several bacterial strains under different fermentation conditions (e.g., pH, O
availability, glycerol purity), three of the screened strains stood out for their high potential to produce valued-added products such as 2,3-butanediol (BDO), 1,3-propanediol (PDO) and ethanol (EtOH). The results indicate that under aerobic conditions,
ACA-DC 1581 produced BDO in high yield (Y
= 0.46 g/g, corresponding to 94% of the maximum theoretical yield; Y
) and titer, while under anaerobic conditions,
NRRL-B 2645 and
FMCC-204 produced PDO (Y
= 0.56 g/g, 93% of Y
) and EtOH (Y
= 0.44 g/g, 88% of Y
), respectively. In the case of
, the regulation of pH proved to be mandatory, due to lactic acid production and a subsequent drop of pH that resulted in fermentation ceasing. In the fed-batch culture of
, the BDO maximum titer reached almost 70 g/L, the Y
and the mean productivity value (Pr
) were 0.47 g/g and 0.4 g/L/h, respectively, while no optimization was imposed. The final BDO production obtained by this wild strain (
) is among the highest in the international literature, although the bioprocess requires optimization in terms of productivity and total cost. In addition, for the first time in the literature, a strain from the species
(
.,
ACA-DC 1196) was reported as a potential BDO producer. The strains as well as the methodology proposed in this study can contribute to the development of a biorefinery that complements the manufacture of biofuels with high-value biobased chemicals.
Staka is a traditional Greek sour cream made mostly from spontaneously fermented sheep milk or a mixture of sheep and goat milk. At the industrial scale, cream separators and starter cultures may ...also be used. Staka is sometimes cooked with flour to absorb most of the fat. In this study, we employed culture-based techniques, amplicon sequencing, and shotgun metagenomics to analyze the Staka microbiome for the first time. The samples were dominated by
or
spp. Most other bacteria were lactic acid bacteria (LAB) from the
and
genera or Gram-negative bacteria from the
,
,
,
-
, and
genera.
,
, or
were the most prevalent genera in the samples, followed by other yeasts and molds like
,
,
,
,
, or
spp. Shotgun metagenomics allowed the species-level identification of
,
,
,
,
,
,
, and
. Binning of assembled shotgun reads followed by recruitment plot analysis of single reads could determine near-complete metagenome assembled genomes (MAGs). Culture-dependent and culture-independent analyses were in overall agreement with some distinct differences. For example, lactococci could not be isolated, presumably because they had entered a viable but not culturable (VBNC) state or because they were dead. Finally, several LAB,
, and
spp. isolates exhibited antimicrobial activities against oral or other pathogenic streptococci, and certain spoilage and pathogenic bacteria establishing their potential role in food bio-protection or new biomedical applications. Our study may pave the way for additional studies concerning artisanal sour creams to better understand the factors affecting their production and the quality.
The human interest in donkey milk is growing due to its nutritional, functional properties and excellent microbiological quality according to published reports. However, more research needs to be ...conducted to assess the above variables from various breeds. In the present study, milk samples were collected from 17 Cypriot and six Arcadian healthy Greek donkeys. The microbiological quality, somatic cell counts (SCC), chemical composition analysis, and antimicrobial activity of the samples was assessed. In addition, clustering and identification of the bacterial composition was performed by RAPD-PCR and 16S rDNA sequencing, respectively. The good microbiological quality of the samples as estimated by the total aerobic mesophilic and psychrotrophic counts, which ranged from 2.18 to 2.71 log CFU/mL and from 1.48 to 2.37 log CFU/mL, respectively, was also verified. SCC were below 4.4 log CFU/mL. However, potential pathogenic species of Staphylococcus aureus, Bacillus cereus, and Clostridium spp. were enumerated in the milk of both breeds. The gross chemical composition showed mean values for fat, protein, and lactose from 0.82% to 1.24%, 1.22% to 1.87%, and 6.01% to 6.78%, respectively. All milk samples exhibited an antimicrobial activity against St. haemolyticus and Listeria monocytogenes, although quality control measures should be taken for health and safety prior to human consumption.
In three different dairies (A, B and C) located in Peloponess region (Southern Greece), traditional Feta cheese trials took place February to March using mixtures of sheep's and goat's milk. Only ...small variations in the evolution of microbial groups were observed during the whole ripening period. The main groups, such as thermophilic cocci, mesophilic lactococci, thermophilic lactobacilli, nonstarter lactic acid bacteria (NSLAB), presumptive
Leuconostoc, enterococci and micrococci, reached their highest levels during the first 16 days, and then declined approximately 1–2 log units until the end of ripening. The remaining groups investigated, comprising yeasts, coliforms and
Escherichia coli, were highest at day 4. The yeasts remained constant, while coliforms and
E. coli decreased sharply and were not detectable after 120 days of ripening. A number of 146 isolates (dairy A) taken from all stages of the manufacturing and ripening process were purified and studied.
Lactobacillus plantarum (58/146) and isolates of related species
Lactobacillus pentosus and
Lactobacillus paraplantarum (16/146) were the most common microorganisms found during cheese ripening.
Streptococcus thermophilus (23/146) and
Lactobacillus delbrueckii subsp.
bulgaricus (20/146) were detected in high levels up to 20 days, and then gradually reduced.
Enterococcus faecium (29/146) was found in all manufacturing and ripening stages.
Goat milk yogurt (GMY) and raisins are popular foods with a favourable nutrient profile. Our aim was to determine the glycaemic index (GI) and postprandial responses to GMY-containing ...angiotensin-converting enzyme inhibitory (ACE-I) peptides carrying the RPKHPINHQ isracidin fragment and two Greek raisin varieties in an acute feeding setting. A total of twelve healthy participants (four male and eight female) consumed breakfast study foods containing 25 g available carbohydrate on seven occasions over a 3- to 9-week period: food 1: D-glucose (25 g) served as the control and was consumed on three separate occasions; food 2: GMY (617·28 g); food 3: Corinthian raisins (37·76 g); food 4: Sultana raisins (37·48 g) and food 5: GMY & C (308·64 g GMY and 18·88 g C). Postprandial glucose was measured over a 2 h period for the determination of GI and glycaemic load (GL). Subjective appetite ratings (hunger, fullness and desire to eat) were assessed by visual analogue scales (100 mm) at 0–120 min. Blood pressure (systolic and diastolic; BP) was measured at baseline and 120 min. GMY provided low GI (26), C and S provided high GI/low GL (75/10 and 70/9, respectively) and GMYC provided low GI (47) values on glucose scale compared with D-glucose. Peak blood glucose rise was significantly lower only for GMY and GMYC compared with reference food (D-Glucose), as well as C and S (P
for all < 0·05). No differences were observed between test foods for fasting glucose, BP and subjective appetite. In conclusion, GMY and GMYC attenuated postprandial glycaemic responses, which may offer advantages to glycaemic control.
Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS), a culture based alternative for microbial diversity studies, is an attractive tool to dereplicate large ...numbers of isolates to a smaller set of representatives for downstream characterization. In the present study, MALDI-TOF MS, combined with a database of reference spectra compiled in previous studies, was applied to identify 88 non-starter lactic acid bacteria (NSLAB) isolated from 18 samples of four different artisanal cheeses produced in the Island of Naxos, Greece, from raw sheep and goat milk without the addition of starters. Eighty-four isolates (95.5%) could be identified directly via MALDI-TOF MS. Lactobacillus brevis and Lactobacillus plantarum were the dominant species, followed by Lactococcus lactis, Leuconostoc mesenteroides Lactobacillus paracasei, Lactobacillus rhamnosus, Pediococcus pentosaceus and Enterococcus faecium. The remaining four isolates represented species present in the database; however, within-species diversity was insufficiently covered. Additionally, pheS sequencing was applied to confirm identification.
•Application of MALDI-TOF MS for the identification of lactic acid bacteria•First fingerprinting of the non-starter lactic acid bacteria of artisanal cheeses produced in the Island of Naxos, Greece•PheS sequencing was performed to validate MALDI-TOF MS identication
Staka is a naturally fermented cream produced from sheep or mixtures of sheep and goat milk in the island of Crete, Greece. This work is the first report on Staka cream microbiota. Initially, counts ...of various bacterial groups were enumerated using selective media and growth conditions. All isolates (101) were subjected to matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) analysis; the spectra obtained were compared with those of an in-house reference database. While 70 isolates were considered identified at the species level, the remaining 31 were not, probably due to a lack of, or an insufficient number of, reference spectra in the MALDI-TOF MS database. Strains representative of the observed diversity among the unidentified MALDI-TOF MS spectra were therefore subjected to pheS and 16S rRNA gene sequencing analysis for further identification. The identification results revealed the presence of Lactobacillus spp., Enterococcus spp., Streptococcus thermophilus and Aerococcus viridans.
•Manufacture of a spreadable, ovine fresh-cheese fortified with saffron extract.•Starter growth was not affected by saffron during cheese manufacture.•Enhanced antioxidant activity of spreadable ...cheese due to saffron supplementation.•Stability of saffron cheese color characteristics during cold storage.•Accepted sensory characteristics of the new product.
Saffron supplemented ovine fresh cheese was studied for its compositional, microbiological, color, antioxidant and sensory characteristics, during cold storage at 4○C for 30 days. The evolution of the total aerobic bacteria and the starter lactococci group, was not remarkably affected, during manufacture, however a significant decrease was observed during storage. In addition, the cheese exhibited a more intensive antimicrobial activity against coliform and enterococci groups, which could be attributed to the saffron presence. Saffron cheese didn’t show any remarkable changes in physicochemical properties. However, an enhanced antioxidant activity was observed on 1st day of manufacture and an increasing proteolysis rate was shown after 20 days of storage. Main changes were observed on color and sensory characteristics. The color coordinate b* was increased with the saffron concentration, suggesting that cheese color gets yellower. The cheese made from milk supplemented with saffron concentration of 50 mg/L was tastefully accepted and brought out traditional sensory characteristics, familiar to Greek consumers.
Probiotic Feta cheese was produced using Propionibacterium freudenreichii subsp. shermanii as an adjunct since it has been shown to induce apoptosis of colon cancer cells in vitro and in vivo through ...the production of propionate and acetate. Microbiological and physicochemical analysis of the cheese was performed through the 60 d period of ripening. Counts of propionibacteria increased until day 7 and then remained constant until the end of ripening (approximately 9 log cfu g−1). Moreover, throughout ripening the presence of P. freudenreichii subsp. shermanii LMG 16424T was confirmed by 16S rRNA gene sequence analysis, while propionic acid was first detected on day 7 and reached a concentration of 52.1 mm on day 60. The ripened cheese containing P. freudenreichii subsp. shermanii was very well accepted by the sensory evaluation panellists. This is the first time that P. freudenreichii subsp. shermanii was studied as a probiotic adjunct in a white-brined cheese.
The technological and probiotic potential of lactic acid bacteria isolated from artisanal Greek yoghurt and fermented milks were evaluated. Fifty-three strains were identified by rep-PCR and 16S rDNA ...sequencing to belong to different Lactobacillus or Enterococcus spp., as well as to Streptococcus thermophilus and Lactococcus lactis. Several strains exhibited promising technological and probiotic properties. Among them, we focused on the production of bioactive peptides with angiotensin-converting enzyme inhibitory (ACE-I) activity during milk fermentation. The majority of strains produced ACE-I peptides when grown in skimmed milk. ACE-I peptides were sometimes sequestered in the original fermented milk sample, but were released and detected following high performance liquid chromatography (HPLC) purification. Mass spectrometry analysis of major peptide peaks in HPLC fractions with ACE-I activity revealed that they derived from the N- or C-terminal of the isracidin peptide region of αS1-casein and two internal peptide fragments, one from β-casein and one from κ-casein.
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