Screening and characterization of β-galactosidase activity in lactic acid bacteria for the valorization of acid whey

Biochemical characterization of a novel β-galactosidase from Pedobacter sp. with strong transglycosylation activity at low lactose concentration

A novel β-galactosidase gene (PbBgal35A) from Pedobacter sp. CAUYN2 was cloned and expressed in Escherichia coli. The gene had an open reading frame of 1917 bp, encoding 638 amino acids with a predicted molecular mass of 62.3 kDa. The deduced amino acid sequence of the gene shared the highest identity of 41% with a glycoside hydrolase family 35 β-galactosidase from Xanthomonas campestris pv. campestris (AAP86763.1). The recombinant β-galactosidase (PbBgal35A) was purified to homogeneity with a specific activity of 65.9 U/mg. PbBgal35A was optimally active at pH 5.0 and 50 °C, respectively, and it was stable within pH 4.5‒7.0 and up to 45 °C. PbBgal35A efficiently synthesized galacto-oligosaccharides from lactose with a conversion ratio of 32% (w/w) and fructosyl-galacto-oligosaccharides from lactulose with a conversion ratio of 21.9% (w/w). Moreover, the enzyme catalyzed the synthesis of galacto-oligosaccharides from low-content lactose in fresh milk, and the GOS conversion ratios of 17.1% (w/w) and 7.8% (w/w) were obtained when the reactions were performed at 45 and 4 °C, respectively. These properties make PbBgal35A an ideal candidate for commercial use in the manufacturing of GOS-enriched dairy products.

Fast and sustainable planar yeast-based bioassay for endocrine disruptors in complex mixtures: Start of cell cultivation to result within one day

High-performance thin-layer chromatography hyphenated with planar multiplex bioassays and high-resolution tandem mass spectrometry contributes to the non-target detection or even identification of active compounds in complex mixtures such as food, feed, cosmetics, commodities, and environmental samples. It can be used to discover previously unknown harmful or active substances in complex samples and to tentatively assign molecular formulas. This method is already faster than the commonly used in vitro assays along with liquid chromatographic separations, but overnight cell cultivation still prevents a planar bioassay from being performed within one day. There is also still potential for optimization in terms of sustainability. To achieve this, the planar bioassay protocols for the detection of androgen-like and estrogen-like compounds were harmonized. The successful minimization of the cell culture volume enabled accelerated cell cultivation, which allowed the bioassay to be performed within one day. This was considered a milestone achieved, as up to 23 samples per plate can now be analyzed from the start of cultivation to the biological endpoint on the same day. Doubling the substrate amount and increasing the pH of the silica gel layer led to a more sensitive and selective bioassay due to the enhanced fluorescence of the formed end-product. The faster and more sustainable bioassay protocol was applied to complex samples such as sunscreen and red wine to detect estrogen-like compounds. The developed method was validated by comparison with a standard method.

Technological and Enzymatic Characterization of Autochthonous Lactic Acid Bacteria Isolated from Viili Natural Starters

Viili, a Finnish ropy fermented milk, is traditionally manufactured through spontaneous fermentation, by mesophilic lactic acid bacteria and yeast-like fungi, or back-slopping. This study evaluated four natural viili starters as sources of lactic acid bacteria for dairy production. Back-slopping activation of the studied viili samples was monitored through pH and titratable acidity measurements and enumeration of mesophilic lactic acid bacteria. Sixty lactic acid bacteria isolates were collected, molecularly identified, and assayed for acidification performance, enzymatic activities, production of exopolysaccharides (EPSs), presence of the histidine decarboxylase (hdcA) gene of Gram-positive bacteria, and production of bacteriocins. A neat predominance of Lactococcus lactis emerged among the isolates, followed by Enterococcus faecalis, Enterococcus faecium, Enterococcus durans, Enterococcus lactis, and Lactococcus cremoris. Most isolates exhibited proteolytic activity, whereas only a few enterococci showed lipase activity. Five isolates identified as L. cremoris, L. lactis, and E. faecalis showed a good acidification performance. Most of the isolates tested positive for leucine arylamidase, whereas only one E. durans and two L. lactis isolates were positive for valine arylamidase. A few isolates also showed a positive reaction for beta-galactosidase and alpha- and beta-glucosidase. None of the isolates produced EPSs or bacteriocins. The hdcA gene was detected in five isolates identified as L. lactis and E. faecium. A few L. cremoris and L. lactis isolates for potential use as starter or adjunct cultures for dairy processing were finally identified.

Study of the probiotic properties of Lacticaseibacillus casei subsp. casei NCIM 5752 and the optimization of whey-based media for the production of its biomass using response surface methodology

In this study, Lacticaseibacillus casei NCIM 5752, a new isolate has been explored for probiotic properties and has shown significant bile salt hydrolase activity and cholesterol-reducing activity (56.7 ± 0.27%) in the presence of bile salts. It also tested negative for the production of lecithinase and gelatinase, indicating its non-pathogenic nature. The test strain was able to tolerate pH of 2.0 and 3.0 with 63.42 and 94.7% of the cells survived after 3 h. L. casei showed auto-aggregation of 85.3% and surface hydrophobicity of 22.5% in xylene and 19.4% in hexane. Paneer whey was explored as a basic raw material for alternative media formulation for growing lactic acid bacteria. Paneer whey was found to contain lactose (4.15%), protein (0.42%), and rich in mineral content. Response surface methodology was employed to optimize the medium composition with three independent variables yeast extract (X1), dextrose (X2), and dipotassium hydrogen phosphate (X3), and the response-Y was set to biomass obtained in terms of log CFU/ml. They were supplemented to paneer whey medium for growing this strain. The second-order polynomial regression model predicted that the maximum cell mass production of 11.30 ± 0.5 log CFU/ml at optimal composition of 16.22 g/L of yeast extract, 19.31 g/L of dextrose, and 2.12 g/L of dipotassium hydrogen phosphate in paneer whey medium. Experiments were conducted to validate the RSM results, and the biomass achieved was 11.27 ± 0.50 log CFU/ml, which is in close agreement with the yield predicted by the RSM. By applying the fermentation strategy, the biomass was increased to 5.56 ± 0.34 g/L dry cell weight corresponding to 11.58 ± 0.24 log CFU/ml. The newly optimized media was significantly cost-effective and produced 26.45% more biomass than the conventional MRS media. This optimized media may find application for the large-scale biomass production of probiotics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03899-z.

Enzyme characterization of lactic acid bacteria isolated from duck excreta

Background and Aim

The production of lignocellulosic biomass waste in the agricultural sector of Indonesia is quite high annually. Utilization of lignocellulosic biomass waste through fermentation technology can be used as feed and biofuel. Fermentation technology requires the involvement of micro-organisms such as bacteria (lactic acid bacteria or LAB). LABs can be isolated from various sources, such as duck excreta. However, there have not been many reports of LAB from duck excreta. The present study aimed to characterize LAB enzymes isolated from duck excreta and obtain LAB enzymes with superior fermentation properties.

Materials and Methods

A total of 11 LAB cultures obtained from duck excreta in Yogyakarta, Indonesia, were tested. Enzyme characterization of each LAB was performed using the API ZYM kit (BioMérieux, Marcy-I'Etoile, France). The bacterial cell suspension was dropped onto the API ZYM™ cupule using a pipette and incubated for 4 h at 37°C. After incubation, ZYM A and ZYM B were dripped onto the API ZYM cupule, and color changes were observed for approximately 10 s under a strong light source.

Results

Esterase activity was moderate for all LABs. The activity of α-chymotrypsin, β-glucuronidase, α-fucosidase, and α-mannosidase was not observed in a total of 10 LAB. The phosphohydrolase and amino peptidase enzyme activity of seven LABs was strong. Only six LAB samples showed protease activity. The glycosyl hydrolase (GH) activity was observed in a total of 8 LAB, while the activity of 2 LAB was strong (Lactococcus lactis subsp. lactis K5 and Lactobacillus brevis M4A).

Conclusion

A total of 2 LABs have superior properties. L. lactis subsp. lactis K5 and L. brevis M4A have a high potential to be used in fermentation. They have the potential for further research, such as their effectiveness in fermentation, lignocellulose hydrolysis, feed additives, molecular characterization to detect specific enzymes, and their specific activities.

The Impacts of Acidophilic Lactic Acid Bacteria on Food and Human Health: A Review of the Current Knowledge

The need to improve the safety/quality of food and the health of the hosts has resulted in increasing worldwide interest in acidophilic lactic acid bacteria (LAB) for the food, livestock as well as health industries. In addition to the use of acidophilic LAB with probiotic potential for food fermentation and preservation, their application in the natural disposal of acidic wastes polluting the environment is also being investigated. Considering this new benefit that has been assigned to probiotic microorganisms in recent years, the acceleration in efforts to identify new, efficient, promising probiotic acidophilic LAB is not surprising. One of these effots is to determine both the beneficial and harmful compounds synthesized by acidophilic LAB. Moreover, microorganisms are of concern due to their possible hemolytic, DNase, gelatinase and mucinolytic activities, and the presence of virulence/antibiotic genes. Hence, it is argued that acidophilic LAB should be evaluated for these parameters before their use in the health/food/livestock industry. However, this issue has not yet been fully discussed in the literature. Thus, this review pays attention to the less-known aspects of acidophilic LAB and the compounds they release, clarifying critical unanswered questions, and discussing their health benefits and safety.

Cordycepin Enhances SIRT1 Expression and Maintains Stemness of Human Mesenchymal Stem Cells

BACKGROUND/AIM

Mesenchymal stem cells (MSCs) have been employed for therapeutic applications of various degenerative diseases. However, the major concern is MSC aging during the in vitro cultivation. Thus, the approach to delay MSC aging was examined in this research by focusing on the expression of Sirtuin 1 (SIRT1), a key anti-aging marker.

MATERIALS AND METHODS

Cordycepin, a bioactive compound derived from Cordyceps militaris, was used to up-regulate SIRT1 and maintain stemness of MSCs. Upon treatment with cordycepin, MSCs were investigated for cell viability, doubling time, key gene/protein expression, galactosidase-associated senescence assay, relative telomere length, and telomerase expression.

RESULTS

Cordycepin significantly increased the expression of SIRT1 in MSCs by activating the adenosine monophosphate activated protein kinase (AMPK)-SIRT1 signalling pathway. Moreover, cordycepin maintained the stemness of MSCs by deacetylating SRY-box transcription factor 2 (SOX2) via SIRT1, and cordycepin delayed cellular senescence and aging of MSCs by enhancing autophagy, inhibiting the activity of senescence-associated-galactosidase, maintaining proliferation rate, and increasing telomere activity.

CONCLUSION

Cordycepin could be used to increase SIRT1 expression in MSCs for anti-aging applications.

Queijo Serra da Estrela PDO Cheese: Investigation into Its Morpho-Textural Traits, Microbiota, and Volatilome

Queijo Serra da Estrela is a PDO Portuguese cheese produced through coagulation of raw ewe’s milk using cardoon (Cynara cardunculus L.) flowers. The present research was aimed at depicting an up-to-date and comprehensive overview of the microbiota of Queijo Serra da Estrela cheese. To this end, viable counting and metataxonomic analysis were carried out on cheeses sampled from four Portuguese artisan producers. Physico-chemical and morpho-textural analyses were also performed, together with the analysis of volatile organic compounds (VOCs). Finally, non-starter lactic acid bacteria (NSLAB) isolated from the cheeses were characterized for their enzymatic activities using a semi-quantitative method. According to the metataxonomic analysis, Lactococcus lactis and Lactococcus piscium were the species occurring at the highest relative abundance. The isolates collected from the cheeses were assigned to Enterococcus durans, Enterococcus faecalis, Enterococcus faecium, Enterococcus lactis, Levilactobacillus brevis, Latilactobacillus graminis, Leuconostoc mesenteroides, and the Lacticaseibacillus casei group. The enzymatic characterization of these cultures highlighted esterase, aminopeptidase, acid phosphatase, beta-galactosidase, alpha-glucosidase, and beta-glucosidase among the major enzymatic activities. Fungal populations were dominated by Debaryomyces hansenii and Kurtzmaniella zeylanoides; however, species rarely found in cheese (e.g., Candida boidinii, Vishniacozyma victoriae, and Starmerella) were also detected. The volatile compounds characterizing the analyzed cheeses were carboxylic acids and esters, followed by carbonyl compounds and alcohols.

Identification of Putative β-Galactosidase Genes in the Genome of Lactobacillus helveticus OSU-PECh-4A

The Lactobacillus helveticus OSU-PECh-4A strain, from the Ohio State University Parker Chair collection, produces exceptional β-galactosidase activity using acid whey as a culture medium, compared with a commercial broth. The strain has a genome sequence of 1,834,843 bp, and its GC content is 36.69%. Using InterProScan v5.50-84.0 software, four genes with putative β-galactosidase function were found.

In vitro and genetic screening of probiotic properties of lactic acid bacteria isolated from naturally fermented cow-milk and yak-milk products of Sikkim, India

A total of 272 isolates of lactic acid bacteria (LAB) were isolated from 22 samples of naturally fermented milk products of Sikkim in India viz. dahi, soft-variety chhurpi, hard-variety chhurpi, mohi and philu, out of which, 68 LAB isolates were randomly grouped on the basis of phenotypic characteristics, and were identified by 16S rRNA gene sequence analysis. Leuconostoc mesenteroides was the most dominant genus, followed by Leuc. mesenteroides subsp. jonggajibkimchii, Lactococcus lactis subsp. cremoris, Lc. lactis, Lc. lactis subsp. hordniae, Lc. lactis subsp. tructae, Enterococcus faecalis, E. italicus and E. pseudoavium. LAB strains were tested for probiotics attributes by in vitro and genetic screening, based on marker genes. LAB strains showed tolerance to pH 3.0, bile salt, resistance to lysozyme and β-galactosidase activity. Enterococcus faecalis YS4-11 and YS4-14 and Lactococcus lactis subsp. cremoris SC3 showed more than 85% of hydrophobicity. Genes clp L and tdc encoding for low pH tolerance, agu A and Ir1516 encoding for bile tolerance, LBA1446 gene encoding for BSH activity, map A, apf, mub 1 and msa encoding for mucosal binding property were detected. Gene mesY for bacteriocin production was detected only in Leuconostoc spp. Based on the in vitro and genetic screening of probiotic attributes, Leuc. mesenteroides; Leuc. mesenteroides subsp. jonggajibkimchii and Lc. lactis subsp. cremoris were tentatively selected for possible probiotic candidates.