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Proteins are important macronutrients with several beneficial health effects. Today, protein-rich diets are gaining popularity, especially in the context of achieving or preserving a healthy weight. However, epidemiological studies associate long-term consumption of proteinrich diets with adverse health outcomes and increased mortality. These adverse effects, at least partially, are mediated by the activity of microbial products obtained by protein fermentation. Undigested food components reach the colon, where the gut microbiota transforms food residues into various metabolites. Given that side chain groups of amino acids are chemically heterogeneous, undigested proteins provide a mix of substrates for microbial fermentation. By using different amino acids, the gut microbiota can produce toxic, genotoxic, and carcinogenic compounds, but also metabolites that impair normal insulin signaling and cardiovascular function. Biological activity of microbial metabolites can contribute to the development of cardiovascular diseases and cancer, which are associated with high-protein diets. In principle, microbiota metabolic products are beneficial for humans and complementary to human metabolism. However, when diet composition is out of balance (e.g. when proteins are present in an excessive amount), microbiota activity shifts towards production of hazardous metabolites. Therefore, the gut microbiota and its activity must be taken into consideration when designing nutritional strategies to promote health.

A thriving community of microorganisms resides in our intestines, forming complex interactions and producing signaling molecules that can affect human physiological processes. Intrinsic and environmental factors modulate the composition of the microbial ecosystem, with diet representing a key factor affecting the formation of gut microbiota. The epidemic of noncommunicable chronic diseases has been associated with the Western diet, which may modulate the gut microbiota, resulting in a detrimental derangement in the microbial community, termed dysbiosis. Dysbiosis may be reverted through dietary interventions and the application of probiotics and prebiotics. Phenolic compounds represent plant-based nutraceuticals, which can be separated into phenolic acids and polyphenols, that exert prebiotic-like effects and may prevent the development of diseases. Besides direct health-promoting activities, beneficial effects of phenolic compounds may be exerted through their interaction with the gut microbiota. A bidirectional relationship between the gut microbiota and phenolic compounds has been observed, as microorganisms are involved in the metabolism of phenolic compounds, whereas phenolic compounds may affect the composition of the microbiota, with selective stimulatory or inhibitory activity towards the growth of microbial members. In this review, insight into the gut microbiota-polyphenols relationship will be given, with a focus on the application of polyphenols for modifying microbiota and promoting health.

Dextransucrase (DS) is a glucosyltransferase (E. C. 2.4.1.5) that catalyzes the transfer of glucosyl residues from sucrose to dextran polymer and liberates fructose. This enzyme isassociated with a wide application range of dextran and oligosaccharides. DS production by Leuconostoc mesenteroidesT3 was optimized using a Central Composite Design under the Response Surface Methodology. Three variables were chosen for optimization: distillery stillage, sucrose and manganese concentration. The results showed that sucrose and manganese concentrations had a positive linear effect on DS production while all variable interactions (stillage-manganese, stillage-sucrose, and sucrose-manganese) had significant influences on the DS production. The maximal DS yield of 3.391±0.131 U cm-3, was obtained in the medium with 64.33 % distillery stillage concentration, 5.30% sucrose concentration and 0.022 % manganese concentration. Our study revealed the potential of distillery stillage combined with sugar beet molasses, supplemented with sucrose and manganese to be employed as a valuable medium growth for lactic acid bacteria and production of DS. Also, taking into consideration the origin of the substrates, utilization of industrial by-products in this way has a great environmental relevance and is in accordance with circular economy.

In this study, a spray drying process of yarrow (Achillea millefolium L.) liquid extracts was optimized by using the response surface methodology. The study aimed to determine the influence of temperature (120-195°C), liquid flow rate (3-16.5 cm3 min-1) and dry matter content in the liquid extract (0.3-1.5 %) on the yield of the drying process, the total polyphenols content and the antioxidant activity of the dry powder. Under the tested conditions the yield varied dramatically and ranged from 8 to 75%, while the effects on the polyphenol content and antioxidant activity were lower. The optimized conditions for the maximum antioxidant activity and maximal yield of the dried extract were as follows: temperature of 130°C, liquid flow rate of 7.5 cm3 min-1 and dry matter content of 1.2%. Under the optimal conditions, the yield was 66 %, while there was a slight decrease in the polyphenol content in the dried extract as compared to that in the liquid extract (145 mg of gallic acid equivalents [GAE] per g of the total dry matter vs. 152 mg GAE g-1, respectively). Consequently, antioxidant activity of the dry powder was only slightly reduced as compared to that of the liquid extract (DPPH neutralization was 58 vs. 64 %, respectively). The dried yarrow powder preserved its antimicrobial activity against pathogenic bacteria Staphylococcus aureus (MIC value of 10 mg cm-3) and Pseudomonas aeruginosa (MIC value of 20 mg cm-3).

Mixed medicinal plant waste was composted with addition of novel bacterial strains belonging to the genera Streptomyces, Paenybacillus, Bacillus and Hymenobacter. The composting was followed by assessment of chemical and biological parameters including C/N ratio, loss of organic matter, phosphorous and potassium content as well as CO2 generation and dehydrogenase activity during 164 days. The selected mesophilic bacterial starters had a potential to significantly reduce the period of mixed herb waste decomposition, from about 6 months to about 2.5 months. Based on the seed germination index of four plants (Fagopirum esculentum, Thymus vulgaris, Cynara scolimus and Lavandula officinalis) the germination and radial root growth of the investigated plants was improved by the inoculated compost. The germination index of all tested species on the mature inoculated composts was in average 60% higher compared to the control compost. The research indicates that the mesophilic starter addition into the herbs waste can contribute to the speed of waste decomposition and lead to the improvement of biofertilization effect of the obtained compost. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 31035]

The production of dextransucrase (DS) by Leuconostoc mesenteroides T3, novel isolate from water kefir grain, was studied and optimized. Bacterial supernatant reached activity of 3.1 U/ml when the culture was grown at 23 C and under static culture condition using classical Tsuchiya medium for DS production. The increase of sucrose concentration to 7% led to an increase of DS activity by 52% compared to the control. Medium with 2% beef extract and 1% yeast extract resulted in 4.52 U/ml, which was 47% higher than in the control (with 2% yeast extract). Finally, the increase of K2HPO4 concentration from 2 to 3% resulted in the increased enzyme activity by 28%. Enzyme purified by polyethylene glycol 400 fractionation displayed maximum activity at 30°C and pH 5.4. Zymogram analysis confirmed the presence of DS of approximately 180 kDa. The addition of divalent cations Ca2+, Mg2+, Fe2+ and Co2+ led to a minor increase of DS activity, while the addition of Mn2+ was the most prominent with 73% increase. These findings classify dextransucrase from Leuconostoc mesenteroides T3 as promising candidate for production of dextran, which has numerous applications in various industries. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 31035]

Cellulases are industrially important enzymes with a potential to convert cellulose into fermentable sugars. Novel bacterial isolate Paenibacillus sp. CKS1 was tested for cellulase activity and the optimal conditions for carboxymethyl cellulase (CMCase) production were determined. Maximum CMCase activity was obtained in the third passage of the bacterial culture after 3 days of incubation at 30°C. Cellobiose and yeast extract was the optimal source of carbon and nitrogen for induction of CMCase activity. In addition, with initial pH 7 of the medium and 40 ml of working volume in 500 ml culture flasks with shaking at 150 rpm, the maximum CMCase activity in a crude culture supernatant reached value of 0.532±0.006 U/ml. For crude CMCase, optimal temperature was 50°C and optimal pH 4.8, respectively. HPLC analysis confirmed the bacterium is capable to hydrolise CMC to glucose and other soluble sugars. [Projekat Ministarstva nauke Republike Srbije, br. TR 31035]

Water kefir is abeverage fermented by a microbial consortium captured in kefir grains. The kefir grains matrix is composed of polysaccharide, primarily dextran, whichis produced by members of the microbial consortium. In this study, we have isolated lactic acid bacteria (LAB) from non-commercial water kefir grains (from Belgrade, Serbia) and screened for dextran production. Among twelve Lisolates threeproduced slime colonies on modified MRS (mMRS) agar containing sucrose instead of glucoseand were presumed to produce dextran. Three LABwere identified based on morphological, physiological and biochemical characteristics and 16S rRNA sequencing as Leuconostoc mesenteroides(strains T1 and T3) and Lactobacillus hilgardii (strain T5). The isolated strains were able to synthesize a substantial amount of dextran in mMRS broth containing 5% sucrose. Maximal yields (11.56, 18.00 and 18.46 g/l) were obtained after 16h, 20h and 32h for T1, T3 and T5, respectively. Optimal temperature for dextran production was 23oC for two Leuconostoc mesenteroides strains and 30oC for Lactobacillus hilgardii strain. The produced dextrans were identified based on paper chromatography while the main structure characteristics of purified dextranwere observed by FT-IR spectroscopy. Our study shows that water kefir grains are a natural source of potent dextranproducing LAB. [Projekat Ministarstva nauke Republike Srbije, br. TR 31035]

Abstract Background Deviations in composition and diversity of intestinal microbiota in infancy have been associated with both the development and recurrence of atopic eczema. Thus, we decided to use a deep and global microarray-based method to characterize the diversity and temporal changes of the intestinal microbiota in infancy and to define specific bacterial signatures associated with eczema. Faecal microbiota at 6 and 18 months of age were analysed from 34 infants (15 with eczema and 19 healthy controls) selected from a prospective follow-up study based on the availability of faecal samples. The infants were originally randomized to receive either Lactobacillus rhamnosus GG or placebo. Results Children with eczema harboured a more diverse total microbiota than control subjects as assessed by the Simpson’s reciprocal diversity index of the microarray profiles. Composition of the microbiota did not differ between study groups at age of 6 months, but was significantly different at age of 18 months as assessed by MCPP (p=0.01). At this age healthy children harboured 3 -fold greater amount of members of the Bacteroidetes (p=0.01). Microbiota of children suffering from eczema had increased abundance of the Clostridium clusters IV and XIVa, which are typically abundant in adults. Probiotic Lactobacillus rhamnosus GG supplementation in early infancy was observed to have minor long-term effects on the microbiota composition. Conclusion A diverse and adult-type microbiota in early childhood is associated with eczema and it may contribute to the perpetuation of eczema.