The Influence of Different Factors on Manganese Incorporation into Saccharomyces cerevisiae

Yeast biomass as well as biomass enriched with trace minerals have been demonstrated to be useful in improving animal health and growth performance. In this work, process for the production of Saccharomyces cerevisiae biomass enriched with manganese, a microelement with antioxidant properties in the form of high bioavailable Mn-protein complex, has been studied. The influences of media composition, Mn2+ concentration and Mn salt were investigated in shaken cultures. The change of biomass and ethanol yields was not observed in molasses media with addition of Mn, while in sucrose media the decrease was observed at Mn2+ concentrations higher than 0.8 mM (added as sulphate) and 0.2 mM (added as chloride). It was established that aeration mode (anaerobic, shaken flask or aerated culture) influences amount and dynamic of Mn incorporation into the yeast biomass, and that this incorporation was S. cerevisiae strain dependent. The Fourier transform infrared (FTIR) spectrophotometry on blank and Mn loaded biomass suggested that carboxyl groups, N-H groups of secondary amide, and sulfonate groups are involved in mechanism of manganese binding

Utjecaj prijenosa gena na evoluciju bakterija mliječne kiseline

In the case of preparing various dairy products, the exploitation of lactic acid bacteria has been essential in the course of past millennia in all known nations. Numerous comparative analyses of gene and genome sequences reveal that the exchange of genetic material within and between bacterial species is far more general and frequent than has previously been thought. Consequently, the horizontal gene transfer between distant species or within the same species is an important factor in the Lactobacillales evolution. Knowledge about the exchange of lactobacillus genetic information through horizontal gene transfer, mobile genetic elements, and its evolution is very important due to characterizations and stability maintenance of autochthonous as well as industrial lactic acid bacteria strains in dairy products that benefit human health.Tijekom tisućljeća u cijelom su svijetu bakterije mliječne kiseline bile prijeko potrebne za pripremu raznovrsnih mliječnih proizvoda. Brojne usporedne analize sekvencija gena i genoma prokariota pokazuju da su izmjene genetičkoga materijala unutar i između bakterijskih vrsta mnogo uobičajenije i češće nego se prije mislilo. Stoga je horizontalni prijenos gena između udaljenih vrsta i unutar iste vrste osobito važan za evoluciju bakterija reda Lactobacillales. Radi dobrobiti za ljudsko zdravlje, izmjena genetičkih informacija tijekom horizontalnog prijenosa gena, pokretni genetički elementi i evolucija laktobacila vrlo su značajni zbog karakterizacije i očuvanja stabilnosti autohtonih, a i industrijskih sojeva bakterija mliječne kiseline u mliječnim proizvodima

Mikrobiološka kvaliteta komercijalnog pekarskog kvasca na hrvatskom tržištu

Komercijalni pekarski kvasac je aktivna biomasa kvasca Saccharomyces cerevisiae kojoj se tijekom procesa proizvodnje, distribucije i skladištenja pridružuju i drugi nenamjenski mikroorganizmi. U radu je ispitana mikrobiološka kvaliteta uzoraka svježih i suhih oblika pekarskog kvasca različitih proizvođača prisutnih na hrvatskom tržištu. Za izolaciju i identifikaciju mikrobne populacije u uzorcima pekarskog kvasca upotrijebljene su klasične mikrobiološke metode, a mikrobni rast određen je brojanjem poraslih kolonija na selektivnim hranjivim podlogama. Rezultati su pokazali da su bakterije mliječne kiseline (BMK) dominantni pridruženi mikroorganizmi pekarskom kvascu, prisutni u koncentraciji od 105 - 108 st/g. U uzorcima kvasca dokazani su i divlji kvasci i koliformne bakterije u koncentraciji od 103, odnosno 104st/g. Suhi pekarski kvasac imao je bolju mikrobiološku kvalitetu budući da u uzorcima nisu dokazane plijesni i bakterija Listeria monocytogenes. Salmonella sp. i Escherichia coli nisu dokazane u nijednom uzorku, dok je Staphylococcus aureus dokazan u 89% uzoraka svježeg te 67% uzoraka suhog kvasca u koncentraciji od oko 101 st/g

Characterization of a S-adenosyl-l-methionine (SAM)-accumulating strain of Scheffersomyces stipitis

S-adenosyl-l-methionine (SAM) is an important molecule in the cellular metabolism of mammals. In this study, we examined several of the physiological characteristics of a SAM-accumulating strain of the yeast Scheffersomyces stipitis (M12), including SAM production, ergosterol content, and ethanol tolerance. S. stipitis M12 accumulated up to 52.48 mg SAM/g dry cell weight. Proteome analyses showed that the disruption of C-24 methylation in ergosterol biosynthesis, a step mediated by C-24 sterol methyltransferase (Erg6p), results in SAM accumulation by S. stipitis M12 compared to the wild-type strain. A comparative proteome-wide analysis identified 25 proteins that were differentially expressed by S. stipitis M12. These proteins are involved in ribosome biogenesis, translation, the stress response, ubiquitin-dependent catabolic processes, the cell cycle, ethanol tolerance, posttranslational modification, peroxisomal membrane stability, epigenetic regulation, the actin cytoskeleton and cell morphology, iron and copper homeostasis, cell signaling, and energy metabolism. [Int Microbiol 2015; 18(2):117-125]Keywords: Scheffersomyces stipitis · S-adenosyl- l-methionine (SAM) · SAM accumulating yeast · C-24 sterol methyltransferase (Erg6p

Evolucija bakterija tijekom stacionarne faze rasta

Metagenomics and advances in molecular biology methods have enhanced knowledge of microbial evolution, metabolism, functions, their interactions with other organisms and their environment. The ability to persist and adapt to changes in their environment is a common lifestyle of 1 % of the known culturable bacteria. Studies in the variety of species have identified an incredible diversity of bacterial lifespan. The holy grail of molecular biology is to understand the integrated genetic and metabolic patterns of prokaryotic organisms like the enteric bacterium Escherichia coli. The usual description of E. coli life cycle comprises four phases: lag, logarithmic, stationary, and death phase, omitting their persistence and evolution during prolonged stationary phase. During prolonged stationary/starvation period, in batch bacterial culture, selected mutants with increased fitness express growth advantage in stationary phase (GASP), which enables them to grow and displace the parent cells as the majority population. The analyses of growth competition of Gram-negative and/or Gram-positive mixed bacterial cultures showed that GASP phenomenon can result in four GASP phenotypes: strong, moderate, weak or abortive. Bacterial stress responses to starvation include functions that can increase genetic variability and produce transient mutator state, which is important for adaptive evolution.Metagenomika i suvremene metode molekularne biologije omogućili su razumijevanje evolucije, metabolizma i funkcije mikroorganizama te njihovih interakcija s drugim organizmima u okolišu. Otpornost i prilagodba na promjene u okolišu uobičajeni su za 1 % poznatih bakterija što se mogu uzgajati u laboratoriju. Istraživanjem različitih bakterijskih vrsta uočena je njihova velika raznolikost. Escherichia coli je „sveti gral“ molekularne biologije u razumijevanju genetike i metaboličkih modela. Životni se ciklus E. coli sastoji od četiri faze: lag, logaritamske, stacionarne i faze odumiranja, zanemarujući bakterijsku postojanost i evoluciju tijekom produljene stacionarne faze. U šaržnoj bakterijskoj kulturi, tijekom produljene stacionarne faze ili vremena izgladnjivanja, preživjele stanice mutanata brže rastu (engl. growth advantage in stationary phase - GASP), pa prerastaju i zamjenjuju većinu roditeljskih stanica. Analiza kompetitivnoga rasta Gram-pozitivnih i/ili Gram-negativnih bakterija, tijekom produljene stacionarne faze u mješovitim kulturama, pokazala je postojanje četiriju GASP fenotipova: jaki, umjereni, slabi i nerazvijeni. Bakterijski odgovor na izgladnjivanje obuhvaća stanične funkcije koje mogu povećati genetičku raznolikost i stvarati mutator stanice bitne za adaptivnu evoluciju bakterija

Potential of bacteria for bioethanol production from lignocellulosic raw materials

Poljoprivreda, šumarstvo i prehrambena industrija izvori su velike količine lignocelulozne biomase, koja može poslužiti kao lako dostupna i jeftina obnovljiva sirovina za dobivanje različitih bioproizvoda. Jedan od takvih proizvoda je i bioetanol. Ovaj rad daje pregled bakterija koje se koriste i/ili istražuju za proizvodnju bioetanola iz lignoceluloznih sirovina. U navedenim istraživanjima proizvodnje bioetanola pomoću bakterija primijenjuju se različiti pristupi kako bi se povećala ekološka i ekonomska efikasnost procesa. Pored uobičajenih bioprocesa, koji se provode u više faza i uz pomoć monokulture, razvijaju se i visokointegrirani (konsolidirani) bioprocesi uz primjenu mikrobnih kokultura.Agriculture, forestry and food industry are sources of large quantities of lignocellulosic biomass, which can be used as an easily accessible and cheap renewable raw material for production of different bioproducts. One of these bioproducts is also bioethanol. This paper provides an overview of bacteria used and/or investigated for bioethanol production from lignocellulose-containing feedstocks. In the research of bioethanol production using bacteria, various approaches are applied in order to increase ecological and economic efficiency of bioprocess. In addition to conventional multi-stage bioprocesses that are carried out using monoculture, highly integrated (consolidated) bioprocesses and applications of microbial cocultures are also in developing stage

Whey - raw material for the production of baker starter-cultures

U radu je ispitana mogućnost proizvodnje bakterija mliječne kiseline (BMK) prikladnih fizioloških karakteristika za pekarstvo na deproteiniziranoj sirutki te uspoređena s proizvodnjom na modificiranoj MRS podlozi. Istraženi su rast i fermentacijska aktivnost bakterija Leuconostoc mesenteroides L-3, Lactobacillus brevis L-62 i Lactobacillus plantarum L-73. Aktivnost navedenih BMK u fermentacijskim podlogama te kiselom tijestu praćena je mjerenjem količine nastale mliječne i octene kiseline. Iako je postignuta aktivnost BMK na sirutki manja nego na MRS, rezultati su pokazali da se deproteinizirana sirutka može koristiti kao osnovni supstrat u proizvodnji gore navedenih bakterija. Najveći prinos biomase (1,7 g/L) i proizvodnja mliječne kiseline (9,15 mg/mL) ostvareni su s bakterijom L. plantarum L-73. Ocjenjivanjem kruha utvrđeno je da su dodatkom startera priređenih na bazi starter-kultura uzgojenih na deproteiniziranoj sirutki poboljšani okus i miris, elastičnost kruha te njegova trajnost u usporedbi s kruhom proizvedenim klasičnim postupkom (uz dodatak monokulture pekarskog kvasca).The possibility of production Lactic acid bacteria (LAB), which are suitable for breadmaking on whey was researched and compared to the results achieved in modified MRS medium. The growth and fermentation activities of Leuconostoc meseteroides L-3, Lactobacillus brevis L-62 and Lactobacillus plantarum L-73 were examined by monitoring lactic and acetic acid production in fermentation broth and in sourdough. Presented results show that deproteinized whey is suitable for LAB production. The best biomass yield (1,7 g/L) and lactic acid production (9,15 mg/mL) was achieved with L. plantarum L-73. Better flavour, elasticity and shelf life of bread made with whey-based starters compared to the classical yeast-monoculture based bread were determined by sensory analysis (DLG method)

The influence of molasses addition on the kinetics of alcoholic fermentation of whey using Kluyveromyces marxianus yeast

U ovom radu praćena je kinetika alkoholne fermentacije pomoću kvasca Kluyveromyces marxianus ZIM 75 na podlogama sastavljenim od sirutke i melase. Fermentacije su provedene u statičkim i semiaerobnim uvjetima na temperaturi 34 °C, a za pripravu podloga korištene su deproteinizirana sirutka i melasa miješane u različitim omjerima tako da je ukupna koncentracija šećera u podlogama bila 5%, 10% i 15%. Provedeni pokusi pokazali su da je podloga koja je sadržavala 10% šećera (saharoza : laktoza = 1:1) optimalna za provođenje fermentacija u statičkim i u semiaerobnim uvjetima. Najbolji prinos etanola u statičkim uvjetima nakon 24 sata fermentacije iznosio je 4,05 % (V/V) dok je u semiaerobnim uvjetima iznosio 4,9 % (V/V). Prirast biomase također je bio bolji u semiaerobnim uvjetima i iznosio je 7,78 g s.tv./L, dok je u statičkim uvjetima prirast biomase iznosio je 3,19 g s.tv./L.Kinetics of alcoholic fermentation by yeast Kluyveromyces marxianus ZIM 75 in various media based on whey and molasses were monitored. The fermentations were performed under static and semiaerobic conditions at 34 °C. Deproteinized whey and molasses were mixed in various proportions to give final sugar mass concentrations of 5%, 10% and 15% in medium. The experiments conducted showed that medium with 10 % of sugar (sucrose:lactose=1:1) is optimal for alcoholic fermentations in static and semiaerobic conditions. The best ethanol yield after 24 hours of fermentation was 4.05 % (V/V) in static conditions and 4.9 % (V/V) in semiaerobic conditions. The biomass yield was 7.78 g d.m./L in semiaerobic conditions and 3.19 g d.m./L in static conditions

Diversity of lactic acid bacteria on organic flours and application of isolates in sourdough fermentation

Organic farming preserves biodiversity and organic products can be the source of many microbial species. The species diversity in organically grown wheat, spelt and rye was investigated in order to find strains suitable for sourdough fermentation. Colonies representing various morphological appearances were isolated and catalase-negative colonies were identified by mass spectrometer Microflex LT ™ MALDI-TOF. The fermentation products (lactic, acetic, formic and phenyllactic acid) were determined by high performance liquid chromatography, while the antifungal activity was determined using an overlay agar method. Wheat flours showed less microbial biodiversity than the rye and spelt flours. The most common genera in the tested flour were Lactobacillus, Pediococcus and Enterococcus. Isolated Lactobacillus farciminis, Pediococcus pentosaceus, Leuconostoc citreum and Lactobacillus brevis showed the best acidification activity. Lactobacillus brevis, Pediococcus pentosaceus, Weissella cibaria and Lactobacillus farciminis showed significant antifungal activity against A. niger 357 and Penicillium sp. 505. The prefermented medium of Lactobacillus farciminis were characterized by high content of lactic and phenyllactic acid

S-adenosyl-L-methionine production by an ergosterol-deficient mutant of Scheffersomyces stipitis

S-adenosyl-L-methionine (SAM, SAMe; AdoMet) is an important methyl donor in many reactions, and recently has attracted much attention due to its expanding application in pharmacy. Efficient ways of its production have been widely researched. In this study it was demonstrated that erg6 mutant of yeast Scheffersomyces stipitis (former Pichia stipitis), obtained by UV mutagenesis and selected by resistance to nystatin, could be used for production of SAM. The mutant strain showed higher ability to accumulate SAM than its parental strain. The experiments demonstrated different dependence of erg6 mutant strain on several cultivation conditions in comparison to parental strain, its higher sensibility to oxidative stress, as well as strong dependence of SAM accumulation on the cell growth phase and supplementation of growth media with methionin