Comparative study on biochemical activity of the intestinal isolates Lactobacillus sp. V3 and Bifidobacterium sp. A71 in different substrates

The two intestinal isolates Lactobacillus sp. V3 and Bifidobacterium sp. A71 were selected for soymilk fermentation according to their acidification activity in soymilk. Beetroot juice and carrot juice were chosen for soymilk supplementation as additional sources of carbohydrates and brewer's yeast as an extra source of nitrogen. The fermentation was carried out for eight hours at 42°C. The fermentation was monitored by standard analytical and microbiological tests for changes of acidity (decreasing pH and increasing acid content), the contents of soluble dry substances, sugars and a-amino acids as well as changes in the number of viable cells. The samples were collected at the beginning and subsequently every two hours until the end of the fermentation. The results showed that there were differences between the tested isolates in terms of their ability to ferment soymilk. The mix with brewer's yeast had a better stimulating effect on the growth of both strains compared to those with juices alone. In addition, the carrot juice stimulated the growth of Bifidobacterium sp. A71 better than beetroot juice, while the opposite effect was found for the growth of Lactobacillus sp. V3

The influence of a cryoprotective medium containing glycerol on the lyophilization of lactic acid bacteria (NOTE)

The aims of liophilization (freeze-drying) of lactic acid bacteria are to preserve pure cultures or to prepare starters for the dairy industry. In both cases, the choice of the cryoprotectant is very important. In this work, samples of Bifidobacterium breve A71 and Bifidobacterium bifidum BbTD were freeze-dried in a new cryoprotective medium containing lactose, gelatine and glycerol (medium B). The reference medium contained saccharose, gelatine and skim milk (medium A). Before liophilization, the eutectic points of both media were determined, because the products must be cooled to a temperature below its freezing point. The success of the cryoprotectants was estimated in terms of the number of surviving organisms after lyophilization. Bifidobacterium breve A71 and Bifidobacterium bifidum BbTD freeze-dried in media A and B showed high survival rates. Bifidobacterium breve A71 showed a greater percentage survival in combination with medium B than with medium A. These results could be utilized in the manufacture of Bifidobacterium breve A71 as a starter in the diary industry because it is a human isolate which, except for acidification, has probiotic activity

Lipase catalyzed synthesis of flavor esters in non-aqueous media: Optimization of the yield of pentyl 2-methylpropanoate by statistical analysis

In this study, the synthesis of pentyl 2-methylpropanoate employing a commercial lipase from Candida rugosa was investigated, the emphasis being placed on analyzing the effects of various process conditions on the yield of ester. The response surface methodology (RSM) and five-level-five-factor central composite rotatable design (CCRD) were used to evaluate the effects of variables, namely the initial water content, 0.0–2.0 % (w/v), the reaction temperature, 35–75 °C, the enzyme concentration, 1.0–5.0 g dm-3, the acid/alcohol mole ratio, 1:2–5:2, and the reaction time, 4–48 h, on the yield (%) of ester. The production of pentyl 2-methylpropanoate was optimized and an ester yield response equation was obtained, enabling the prediction of ester yields from known values of the five main factors. It seems that the enzyme concentration, reaction time and acid/alcohol mole ratio predominantly determine the conversion process, while the amount of added water amount had no significant influence on the ester yield. Conversion of around 92 % of the substrate to ester could be realized using a concentration of lipase as low as 4.0 g dm-3 and in a relatively short time (26 h) at 35 °C, when a high substrate mole ratio of 2.5 was used

Efikasnost različitih metoda za određivanje ostataka organofosfata u fermentisanim uzorcima žita

In the present work, the efficiencies of three different sample preparation methods for GC/ MS determination of pirimiphos-methyl and chlorpyrifos-methyl residues in wheat (Triticum spelta) samples fermented by Lactobacillus plantarum were compared. All three methods were based on methanol:acetone=1:1 extraction, while further purification of the obtained samples was altered. First purification was through a column containing a mixture of aluminium oxide and activated charcoal slurry-packed and eluted with dichlormethane, the second was purification on a florisil column slurry-packed and eluted with ethyl acetate:acetone=4:1, while the third was based on a combination of the former two methods, i.e. clean-up through columns filled with a mixture of aluminum oxide and activated charcoal slurry-packed and eluted with ethyl acetate:acetone=4:1. The second method was found the most effective for obtaining satisfactory recoveries at four fortification levels. For pirimiphos-methyl, recoveries were in the range of 91.3-96.0% and had good reproducibility, i.e. RSD ranging from 2.2-4.1%, while the corresponding range for chlorpyrifos-methyl was 81.6-88.2%, and the RSD range 2.5-5.4%. The chosen method was further optimized in order to establish the optimum volume of elution solvent used during the clean-up procedures. The highest recoveries of 93.7±3.5% for pirimiphos- methyl and 85.3±2.5% for chlorpyrifos-methyl were obtained after elution with 25 ml volume of solvent. Considering all, simple, efficient and reliable GC/MS detection of pirimiphosmethyl and chlorpyrifos-methyl residues in wheat grain substrate altered by fermentation with L. plantarum was achieved by the two-steps extraction with 25 ml of methanol:acetone=1:1 solvent mix for 30 min, followed by a clean-up procedure through a glass column with florisil coupled with elution by 25 ml of ethyl acetate:acetone=4:1.Poređene su efikasnosti tri različite metode pripreme uzoraka za određivanje ostataka pirimifos-metila i hlorpirifos-metila u uzorcima pšenice (Triticum spelta) fermentisane sa Lactobacillus plantarum. Sve tri metode zasnivale su se na metanolsko-acetonskoj (1:1) ekstrakciji dok su se procedure prečišćavanja dobijenih ekstrakata razlikovale. Prva metoda bila je prečišćavanje kroz kolonu punjenu smešom aluminijum-oksida i aktivnog uglja u kombinaciji sa dihlormetanom kao eluentom, druga prečišćavanje kroz kolonu punjenu florisilom u kombinaciji sa smešom etil-acetata i acetona (4:1) kao eluentom, dok se treća zasnivala na kombinaciji prve dve, tj. prečišćavanju kroz kolonu punjenu smešom aluminijum-oksida i aktivnog uglja u kombinaciji sa smešom etil-acetata i acetona (4:1) kao eluentom. Druga testirana metoda pokazala se kao najefikasnija, pri čemu su dobijeni prinosi pirimifos-metila u opsegu 91,3-96,0% za četiri koncentraciona nivoa obogaćivanja, sa RSD% u opsegu 2,2-4,1%, dok su za hlorpirifos-metil ovi prinosi bili u opsegu 81,6-88,2% sa RSD% u opsegu 2,5-5,4%. Odabrana metoda je dodatno optimizovana variranjem različitih zapremina korišćenog eluenta. Najveći prinos metode za oba ispitivana pesticida postignut je pri zapremini eluenta od 25 ml (93,7±3.5% za pirimifos-metil i 85,3±2,5% za hlorpirifos-metil). Predložena metoda, bazirana na 30-minutnoj ekstrakciji sa 25 ml smeše metanol:aceton=1:1, prečišćavanju na florisilskoj koloni i eluiranju sa 25 ml smeše etilacetat: aceton=4:1, pokazala se kao efikasna, jednostavna i pouzdana metoda za određivanje ostataka ispitivanih organofosfata u fermentisanom žitnom supstratu

Efficiencies of different methods for determination of organophosphate pesticide residues in fermented wheat substrate

In the present work, the efficiencies of three different sample preparation methods for GC/MS determination of pirimiphos-methyl and chlorpyrifos-methyl residues in wheat (Triticumspelta) samples fermented by Lactobacillus plantarum were compared. All three methods werebased on methanol:acetone=1:1 extraction, while further purification of the obtained sampleswas altered. First purification was through a column containing a mixture of aluminiumoxide and activated charcoal slurry-packed and eluted with dichlormethane, the second waspurification on a florisil column slurry-packed and eluted with ethyl acetate:acetone=4:1, whilethe third was based on a combination of the former two methods, i.e. clean-up through columnsfilled with a mixture of aluminum oxide and activated charcoal slurry-packed and elutedwith ethyl acetate:acetone=4:1. The second method was found the most effective for obtainingsatisfactory recoveries at four fortification levels. For pirimiphos-methyl, recoveries werein the range of 91.3-96.0% and had good reproducibility, i.e. RSD ranging from 2.2-4.1%, whilethe corresponding range for chlorpyrifos-methyl was 81.6-88.2%, and the RSD range 2.5-5.4%.The chosen method was further optimized in order to establish the optimum volume of elutionsolvent used during the clean-up procedures. The highest recoveries of 93.7±3.5% for pirimiphos-methyl and 85.3±2.5% for chlorpyrifos-methyl were obtained after elution with 25 mlvolume of solvent. Considering all, simple, efficient and reliable GC/MS detection of pirimiphosmethyland chlorpyrifos-methyl residues in wheat grain substrate altered by fermentation withL. plantarum was achieved by the two-steps extraction with 25 ml of methanol:acetone=1:1solvent mix for 30 min, followed by a clean-up procedure through a glass column with florisilcoupled with elution by 25 ml of ethyl acetate:acetone=4:1

Effect of fermentation conditions on lipase production by Candida utilis

A wild yeast strain isolated from spoiled soybean oil and identified as Candida utilis initially presented rather low lipase activity (approximately 4 IU dm-3) in submerged culture in a universal yeast medium containing 2 % malt extract. Stu­dies were undertaken to improve the lipase production. The best yields of lipase were obtained with a medium supplemented with caprylic and oleic acids as indu­cers, but higher concentrations of the former (> 0.5 %) had a negative effect on the lipase production and cell growth. The type of nitrogen source seemed also to be very important. The highest lipolytic activity of 284 IU dm-3 was achieved after 5 days of fermentation in a medium containing oleic acid and hydrolyzed casein as carbon and nitrogen sources, respectively, and supplemented with Tween 80®. It was shown that optimization of the fermentation conditions can lead to a significant improvement in the lipase production (more than 70-fold higher compared to the initial value obtained in the non-optimized medium)

Bimetallic alginate nanocomposites: New antimicrobial biomaterials for biomedical application

Two bimetallic (Zn/Cu) alginate based nanocomposites, impregnated with carbonate or phosphate mineral phase, were prepared by a facile procedure. Mineralized samples exhibited different morphologies and properties when compared to the non-mineralized sample. Antimicrobial testing against Escherichia coil, Staphylococcus aureus and Candida albicans showed that mineralized samples are more efficient than non-mineralized in elimination of microorganisms. The results of this study suggest that bimetallic mineralized alginates could be potentially used as affordable, easy to produce antimicrobial materials

Mineralized agar-based nanocomposite films: Potential food packaging materials with antimicrobial properties

New mineralized, agar-based nanocomposite films (Zn-carbonate and Zn-phosphate/agar) were produced by a combination of in situ precipitation and a casting method. The presence of minerals significantly influenced the morphology, properties and functionality of the obtained nanocomposites. Reinforcement with the Zn-mineral phase improved the mechanical properties of the carbonate-mineralized films, but had a negligible effect on the phosphate-mineralized samples. Both nanocomposites showed improved optical and thermal properties, better Zn(II) release potential in a slightly acidic environment and exhibited antimicrobial activity against S. aureus. These results suggest that Zn-mineralized agar nanocomposite films could be potentially used as affordable, eco-friendly and active food packaging materials