Candida Maltosa Research Articles

Biological activities of selected basidiomycetes from Yemen.

In a previous paper we demonstrated the results of biological screening of Yemeni basidiomycetes. The present study was aimed to investigate the antimicrobial and the antioxidant activity of further basidiomycetes collected in Yemen. Dichloromethane, methanol and aqueous extracts of the fruiting bodies of 25 species were screened in vitro for their antibacterial activities against three Gram-positive bacteria (Staphyloccocus aureus, Bacillus subtilis, Micrococcus flavus) and two Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa), against six human fungal pathogens (Candida albicans, Candida krusei, Aspergillus fumigatus, Mucor sp., Microsporum gypseum, Trichophyton mentagrophytes) and against one non human pathogenic fungus (Candida maltosa). The results indicated that 75 extracts exhibited activity against one or more of the bacteria. The methanol extracts of Agaricus cf. bernardii, Agrocybe pediades, Chlorophyllum molybdites, Coriolopsis polyzona, Ganoderma xylonoides, Pycnoporus sanguineus, Trametes lactinea and Trametes cingulata showed activity against all tested bacteria. The highest antibacterial activity was exhibited by methanol extracts from Chlorophyllum molybdites, Ganoderma xylonoides and Trametes cingulata and Agaricus cf. bernardii, Agrocybe pediades, Coriolopsis polyzona, Pycnoporus sanguineus and Trametes lactinea. The methanol extracts of Chlorophyllum molybdites, Ganoderma xylonoides and Pycnoporus sanguineus showed considerable antifungal activities against the tested fungal strains. Strong antioxidative effects employing the DPPH assay were exhibited by methanol extracts from Chlorophyllum molybdites, Ganoderma xylonoides, Hexagonia velutina, Pycnoporus sanguineus, Trametes lactinea and Trametes cingulata. Our previous and presented studies about 48 basidiomycetes collected in Yemen provide evidence that basidiomycetes from the Arabic region so far should attract more attention as potential source for new biologically active agents.

Yeasts from phylloplane and their capability to produce indole-3-acetic acid

Yeasts were isolated from the phylloplane of various plant species collected from seven provinces in Thailand. A total of 114 yeast strains and 10 strains of a yeast-like fungus were obtained by enrichment isolation from 91 out of 97 leaf samples (93.8 %). On the basis of the D1/D2 domain of the large subunit rRNA gene sequence similarity, 98 strains were identified to be of 36 yeast species in 18 genera belonging to Ascomycota viz. Candida, Clavispora, Cyberlindnera, Debaryomyces, Hanseniaspora, Hyphopichia, Kazachstania, Kluyveromyces, Kodamaea, Lachancea, Metschnikowia, Meyrozyma, Pichia, Starmerella, Torulaspora and Wickerhamomyces, and to Basidiomycota viz. Sporidiobolus and Trichosporon. Three strains were found to represent two novels Candida species which were previously described as C. sirachaensis and C. sakaeoensis. Ten strains of yeast-like fungus were identified as Aureobasidium pullulans of the phylum Ascomycota. Ascomycetous yeast species accounted altogether for 98.0 % of the 98 strains. The prevalent species was Candida tropicalis with a low frequency of isolation (14.3 %). Diversity of yeasts other than ballistoconidium-forming yeast in phylloplane in a tropical country in Asia has been reported for the first time. All strains obtained were accessed for the capability to produce IAA and result revealed that 39 strains in 20 species, one strain each of an undescribed and a novel species, and two unidentified strains showed the capability of producing IAA when cultivated in yeast extract peptone dextrose broth supplemented with 0.1 % L-tryptophan. All five strains of Candida maltosa produced relatively high concentrations of IAA.

Antifungal activities of volatile substances generated by yeast isolated from Iranian commercial cheese

A yeast isolate, Candida maltosa NP9, was obtained from a fermented food, Iranian commercial cheese. The strain grown on YPD agar inhibited spore germination of Aspergillus brasiliensis by vapor-agar contact method. Seven volatile compounds generated from the strain were detected by SPME–GC/MS analysis, and three of them were identified as isoamyl alcohol, isoamyl acetate, and phenethyl alcohol by GC/MS analysis. Although phenethyl alcohol did not inhibit the germination at 160 μl/dish by 48 h exposure, isoamyl alcohol fungicidally inhibited at 80 μl/dish and isoamyl acetate fungiostatically inhibited at 160 μl/dish. In antifungal spectra with 15 kinds of filamentous fungi, isoamyl alcohol inhibited the germination of all strains at 20 μl/dish, while isoamyl acetate did not inhibit the germination of three strains even at 160 μl/dish. We demonstrated that C. maltosa NP9 from the fermented food generated volatile isoamyl acetate and isoamyl alcohol to inhibit the germination of those fungi.

Biosensor analyzer for BOD index express control on the basis of the yeast microorganisms Candida maltosa, Candida blankii, and Debaryomyces hansenii

The parameters of biosensors based on the yeast strains Candida maltosa VKM Y-2359, Candida blankii VKM Y-2675, and Debaryomyces hansenii VKM Y-2482 for biochemical oxygen demand (BOD) detection are compared. The catalytic activity of the strains was analyzed in relation to the growth phase. The possibility of using D. hansenii as a basis for receptor element of a biosensor for BOD detection in municipal and biotechnological wastewaters was shown.

In vitro antibacterial activity of three medicinal plants- Boswellia (Luban) species

Objective To study in vitro antibacterial and antifungal activity of hot water and methanolic extracts of the three medicinal plants- Boswellia (Luban) species. Methods Three selected plants were collected from different localities of Soqotra (Republic of Yemen), Dohfar (Sultanate of Oman) and Republic of Somalia. The plants were dried and extracted with two different solvents (methanol and hot water) to yield six crude extracts. The obtained extracts were tested for their antibacterial activity against eleven different bacterial strains and two fungi using the standard well-diffusion and micro-dilution methods. The following microorganisms were used: methicillin-resistant Staphylococcus aureus (ATCC 6538), muti-drug resistant Pseudomonas aeruginosa (ATCC 27853), enterohemorrhagic Escherichia coli (0157 EHEC), Salmonella typhi, Proteus vulgaris, Klebsiella pneumoniae, Bacillus subtilus (ATCC 6059, reference strain), Streptococcus pneumoniae, Klebsella pneumonia, MRSA, Corynebacterium, Corynebacterium diphtheriae and two fungus: Candida maltosa and Candida albicans . Results The different extracts possessed different inhibitory activity against different types of bacterial species. The patterns of inhibition varied with the plant extract, the solvent used for extraction and the organisms tested. The antimicrobial activity exhibited by the methanolic extracts of Boswellia sacra from the Suqotra and Dhofar regions was greater than that of Boswellia frereana collected from Somalia. The methanolic extract of the oleo-gum-resin showed higher efficacy to inhibit all the tested bacterial strains than the methanolic extract of frankincense-resin . The Boswellia frereana collected from Somalia showed lower activity compared with the two other Boswellia species. The plant extracts showed bacteriostatic activity at lower concentrations and bactericidal activity at higher concentrations. Neither water nor methanolic extracts showed any activity against the fungi Candida maltosa and Candida albicans . Conclusions It can be concluded that the methanolic extracts of Boswellia (Luban) possess the highest antibacterial activity. Neither water nor methanolic extracts show any activity against Candida maltosa and Candida albicans.

Xylitol production from xylose mother liquor: a novel strategy that combines the use of recombinant Bacillus subtilis and Candida maltosa

BackgroundXylose mother liquor has high concentrations of xylose (35%-40%) as well as other sugars such as L-arabinose (10%-15%), galactose (8%-10%), glucose (8%-10%), and other minor sugars. Due to the complexity of this mother liquor, further isolation of xylose by simple method is not possible. In China, more than 50,000 metric tons of xylose mother liquor was produced in 2009, and the management of sugars like xylose that present in the low-cost liquor is a problem.ResultsWe designed a novel strategy in which Bacillus subtilis and Candida maltosa were combined and used to convert xylose in this mother liquor to xylitol, a product of higher value. First, the xylose mother liquor was detoxified with the yeast C. maltosa to remove furfural and 5-hydromethylfurfural (HMF), which are inhibitors of B. subtilis growth. The glucose present in the mother liquor was also depleted by this yeast, which was an added advantage because glucose causes carbon catabolite repression in B. subtilis. This detoxification treatment resulted in an inhibitor-free mother liquor, and the C. maltosa cells could be reused as biocatalysts at a later stage to reduce xylose to xylitol. In the second step, a recombinant B. subtilis strain with a disrupted xylose isomerase gene was constructed. The detoxified xylose mother liquor was used as the medium for recombinant B. subtilis cultivation, and this led to L-arabinose depletion and xylose enrichment of the medium. In the third step, the xylose was further reduced to xylitol by C. maltosa cells, and crystallized xylitol was obtained from this yeast transformation medium. C. maltosa transformation of the xylose-enriched medium resulted in xylitol with 4.25 g L-1·h-1 volumetric productivity and 0.85 g xylitol/g xylose specific productivity.ConclusionIn this study, we developed a biological method for the purification of xylose from xylose mother liquor and subsequent preparation of xylitol by C. maltosa-mediated biohydrogenation of xylose.

Microorganisms form exocellular structures, trophosomes, to facilitate biodegradation of oil in aqueous media

Cytochemical staining and microscopy were used to study the trophic structures and cellular morphotypes that are produced during the colonization of oil-water interfaces by oil-degrading yeasts and bacteria. Among the microorganisms studied here, the yeasts (Schwanniomyces occidentalis, Torulopsis candida, Candida tropicalis, Candida lipolytica, Candida maltosa, Candida paralipolytica) and two representative bacteria (Rhodococcus sp. and Pseudomonas putida) produced exocellular structures composed of biopolymers during growth on petroleum hydrocarbons. Four of the yeasts including S. occidentalis, T. candida, C. tropicalis and C. maltosa excreted polymers through modified sites in their cell wall ('canals'), whereas C. lipolytica and C. paralipolytica and the two bacterial species secreted polymers over the entire cell surface. These polymers took the form of fibrils and films that clogged pores and cavities on the surfaces of the oil droplets. A three-dimensional reconstruction of the cavities using serial thin sections showed that the exopolymer films isolated the ambient aqueous medium together with microbial cells and oil to form both closed and open granules that contained pools of oxidative enzymes utilized for the degradation of the oil hydrocarbons. The formation of such granules, or 'trophosomes,' appears to be a fundamental process that facilitates the efficient degradation of oil in aqueous media.

Synthesis of distinctly different sets of antimicrobial activities by elicited plant cell suspension cultures

The aim of this study was to evaluate the potential of plant suspension cultures for the production of antimicrobial activities. The extracellular, intracellular and cell wall bound fractions of 16 heterotrophic, photoautotrophic and photomixotrophic plant cell suspension cultures each treated with nine different elicitors were tested for the elicitor dependent production of antimicrobial activities. Distinctly different patterns of bioactivities directed against a panel of human isolates including Gram-positive (Bacillus subtilis, Staphylococcus aureus) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria as well as fungi (Candida maltosa) were identified for all except the two autotrophic cell cultures. The intracellular fractions of elicited cell cultures were more active than extracellular fractions while cell wall bound fractions showed almost no activities. The intracellular fraction of heterotrophic Lavendula angustifolia cells elicited with a preparation of Pseudomonas syringae was the most active fraction against Candida maltosa. The intracellular fraction of photomixotrophic Arabidopsis thaliana cells elicited with salicylic acid was active against all test isolates. An antimicrobial protein could be identified and partially purified from this culture. Our findings suggest that elicited plant cell cultures may present a new promising alternative source of antimicrobial proteins.

Isolation of Phenol-Degrading Yeast Pd6 and its Biodegradation of Substitute Phenols*

An effective phenol-degrading yeast Pd6 was isolated from sewage and soil of oil refi nery,and it was identified as Candida maltosa based on its phenotypic features and similarity of 26S rRNA gene sequences.The strain was found able to use phenol as sole carbon and energy source,and it could degrade phenol at a high concentration of 1 500 mg/L.Moreover,by adding organic carbon and nitrogen sources it could largely increase its phenol-degrading ability.It could also degrade other nine kinds of substitute phenols,including monochlorophenols,at a relatively high rate,except 2-chlorophenol.Since the monochlorophenols are conventional non-growth substrates,the biodegradation of 3-and 4-chlorophenol was further investigated,which showed that both 3-and 4-chlorophenol could be co-metabolized with phenol as the only carbon source.

The Alcohol Dehydrogenase System in the Xylose-Fermenting Yeast Candida maltosa

BackgroundThe alcohol dehydrogenase (ADH) system plays a critical role in sugar metabolism involving in not only ethanol formation and consumption but also the general “cofactor balance” mechanism. Candida maltosa is able to ferment glucose as well as xylose to produce a significant amount of ethanol. Here we report the ADH system in C. maltosa composed of three microbial group I ADH genes (CmADH1, CmADH2A and CmADH2B), mainly focusing on its metabolic regulation and physiological function.Methodology/Principal FindingsGenetic analysis indicated that CmADH2A and CmADH2B tandemly located on the chromosome could be derived from tandem gene duplication. In vitro characterization of enzymatic properties revealed that all the three CmADHs had broad substrate specificities. Homo- and heterotetramers of CmADH1 and CmADH2A were demonstrated by zymogram analysis, and their expression profiles and physiological functions were different with respect to carbon sources and growth phases. Fermentation studies of ADH2A-deficient mutant showed that CmADH2A was directly related to NAD regeneration during xylose metabolism since CmADH2A deficiency resulted in a significant accumulation of glycerol.Conclusions/SignificanceOur results revealed that CmADH1 was responsible for ethanol formation during glucose metabolism, whereas CmADH2A was glucose-repressed and functioned to convert the accumulated ethanol to acetaldehyde. To our knowledge, this is the first demonstration of function separation and glucose repression of ADH genes in xylose-fermenting yeasts. On the other hand, CmADH1 and CmADH2A were both involved in ethanol formation with NAD regeneration to maintain NADH/NAD ratio in favor of producing xylitol from xylose. In contrast, CmADH2B was expressed at a much lower level than the other two CmADH genes, and its function is to be further confirmed.

Synthesis of model morpholine derivatives with biological activities by laccase‐catalysed reactions

The efficient enzyme-catalysed reaction of morpholines as model structures for bioactive compounds with para-dihydroxylated aromatic systems was carried out using the oxidoreductase laccase and atmospheric oxygen to produce eight novel morpholine-substituted aromatics. The laccase of Myceliophthora thermophila was used for cross-linking morpholines containing primary or secondary amino groups with para-dihydroxylated laccase substrates. We demonstrate that not only primary amino groups, but also secondary amino groups, are able to couple with para-dihydroxylated aromatic systems in laccase-catalysed reactions. The resulting model products (yields up to 80%) were isolated, structurally characterized and tested for their antibacterial, antifungal and cytotoxic activities. Four of the eight products showed low to moderate growth inhibition against several Gram-positive and -negative bacterial strains and against the yeasts Candida maltosa and Candida albicans. The antibacterial and antifungal activities were determined by an agar disc diffusion test and a modified method according to the EUCAST discussion document E.Dis 7.1 [Rodríguez-Tudela et al. (2003) Clin. Microbiol. Infect. 9, i-viii] for the evaluation of MIC (minimal inhibitory concentration). Differences in cytotoxicity against the human urinary bladder carcinoma cell line 5637 are discussed.

Regulation of Acanthamoeba castellanii alternative oxidase activity by mutual exclusion of purine nucleotides; ATP's inhibitory effect

The effects of different adenine and guanine nucleotides on the cyanide-resistant respiration (i.e. alternative oxidase (AcAOX) activity) of mitochondria from the amoeba A. castellanii mitochondria were studied. We found that guanine nucleotides activate AcAOX to a greater degree than adenine nucleotides, and that nucleoside monophosphates were more efficient activators than nucleoside di- or triphosphates. The extent of the nucleotides' influence on AcAOX was dependent on the medium's pH and was more pronounced at pH 6.8, which is optimal for AcAOX activity. In contrast to other purine nucleosides, we demonstrate, for the first time, that ATP has an inhibitory effect on AcAOX activity. Since we also observed the inhibition by ATP in the mitochondria of another protozoon, such as Dictyostelium discoideum, and the yeast, Candida maltosa, it may be a regulatory feature common to all purine nucleotide-modulated non-plant AOXs. The physiological importance of this discovery is discussed. Kinetic data show that the binding of GMP (a positive allosteric effector) and the binding of ATP (a negative allosteric effector) to AcAOX are mutually exclusive. ATP's inhibition of the enzyme can be overcome by sufficiently high concentrations of GMP, and conversely, GMP's stimulation can be overcome by sufficiently high concentrations of ATP. However, an approximately three times lower concentration of GMP compared to ATP gives a half maximal effect on AcAOX activity. This is indicative of a higher binding affinity for the positive effector at the same or, at least overlapping, nucleotide-binding sites on AcAOX. These results suggest that AcAOX activity in A. castellanii mitochondria might be controlled by the relative intracellular concentrations of purine nucleotides.

Biosorption of Nickel by Yeasts in an Osmotically Unsuitable Environment

The tolerance, sorption of nickel(II) ions, and changes in the production and composition of exopolymers of eight yeast strains grown under nickel presence with/without NaCl were studied. Strains of Pichia anomala and Candida maltosa known as the most resistant yeasts against nickel tolerated up to 3 mM Ni2+. NaCl addition decreased both the resistance of the yeast strains toward nickel ions and the sorption of metal ions into cells. All yeasts absorbed nickel predominantly into exopolymers (glycoproteins) and on the surface of cells. However, while the amount of polysaccharide moieties of exoglycoproteins of most of the resistant yeasts was induced by stress conditions, the ratio polysaccharide/protein in the exopolymers remained unchanged in the sensitive species Cystofilobasidium. The exopolymer composition might play a key role in yeast adaptation to stress conditions caused by heavy metal ions.

Identification of Two SET Domain Proteins Required for Methylation of Lysine Residues in Yeast Ribosomal Protein Rpl42ab

We show that the Saccharomyces cerevisiae ribosomal protein Rpl42ab (the identical product of the RPL42A and RPL42B genes) is monomethylated at Lys-40 and Lys-55. The methylation of Lys-40 is dependent upon the Ybr030w gene product; the methylation of Lys-55 is dependent upon the Set7 gene product. Ybr030w and SET7 genes both encode SET domain containing proteins homologous to known protein lysine methyltransferases, suggesting that their products are the specific enzymes responsible for the monomethylation of the two sites in Rpl42ab. We thus designate Ybr030w as Rkm3 and Set7 as Rkm4. Yeast strains with deletions in both the Ybr030w and SET7 genes produce unmethylated Rpl42ab. A slow growth phenotype was seen for the SET7 deletion strain and the double knock-out when grown in low concentrations of the eukaryotic protein synthesis inhibitor, cycloheximide. These results suggest that modification of Rpl42ab at Lys-55 can fine-tune its structure to avoid inhibition. An intact mass fragmentation approach ("top down mass spectrometry") was used to quantitate the extent of methylation of Rpl42ab. In wild-type strains, it was found that 78% was monomethylated at both Lys-40 and Lys-55 and that 22% was a mixture of species with either Lys-40 or Lys-55 monomethylated. The top down approach was also used to reevaluate the methylation sites of Rpl12ab. We found that the yeast Rpl12ab protein is dimethylated at the N-terminal proline residue, trimethylated at Lys-3 by Rkm2, and monomethylated at Arg-66.

Adsorption of Sodium Dodecylbenzenesulphonate (SDBS) on Candida maltosa EH 15 Strain: Influence on Cell Surface Hydrophobicity and n-alkanes Biodegradation

The effect of exogenously added sodium dodecylbenzenesulphonate (SDBS) surfactant on biodegradation of a mixture of straight-chain aliphatic hydrocarbons (dodecane and hexadecane) and resulting cell surface hydrophobicity changes of Candida maltosa EH 15 were investigated. Results indicated that up to 75 mg/L SDBS improves the biodegradation potential of examined yeast. A decrease in hydrophobicity was observed when SDBS was supplemented in higher concentrations, having strong impact on biodegradation rates. Phase distribution of surfactant molecules was investigated using methylene blue active substances method (MBAS), accompanied by surface and interfacial tension measurements. Studies showed that portion of SDBS molecules adsorbed on cell surface may play significant role in interaction between anionic surfactant and yeast cells, having influence on biodegradation rates.

Degradation of phenylalkanes and characterization of aromatic intermediates acting as growth inhibiting substances in hydrocarbon utilizing yeast Candida maltosa

Phenylalkanes constitute up to 28% of refined gasoline fuel oil. Because of the widespread use of petroleum, oil and gasoline and the environmental risks associated with accidental spills, the ability to degrade these compounds is a major goal of environmental research. We here report our investigation in the use of yeast to degrade phenylalkanes. Among the studied strains of the genera Candida, Hansenula, Pichia, Saccharomyces and Arxula the alkane-assimilating ones grew on phenylalkanes with alkyl side chains longer than C7, utilizing them as sole carbon and energy source. Detailed studies on phenylalkane metabolism were carried out with Candida maltosa SBUG 700. During incubation of this yeast with phenyldecane, phenyloctane and phenylhexane 4-phenylbutanoic acid, 4-phenyl-3-butenoic acid and phenylacetic acid were produced whereas benzoic acid was the only detectable degradation product of phenylnonane and phenylheptane. Phenylacetic acid and benzoic acid were accumulated in high amounts due to the inability of C. maltosa to oxidize these acids further. Oxidation of phenylalkanes was inhibited in the presence of 1-aminobenzotriazole acting as inhibitor of cytochrome P450. Furthermore, toxic effects of benzoic acid and phenylacetic acid amplified by fallen pH values of growth medium strongly inhibited the metabolism of phenylalkanes as well as glucose assimilation and this led to incomplete phenylalkane degradation.

Phenol and n-alkanes (C12 and C16) utilization: influence on yeast cell surface hydrophobicity

This study was focused on the role of two types of diametrically different carbon sources, n-alkanes represented by a mixture of dodecane–hexadecane, and phenol on modification of the cell surface hydrophobicity. Capabilities of using either solely hydrocarbons or hydrocarbons in the mixture with phenol as well as phenol itself by yeast species Candida maltosa, Yarrowia lipolytica and Pichia guilliermondii were investigated. Studies were complemented by cell biomass formation measurements. The corresponding cell surface hydrophobicity was assessed by microbial adhesion to the hydrocarbon test (MATH). Degradation of phenol was examined using GC-SPE technique, whereas hydrocarbons were extracted prior to gravimetric determination. Results obtained indicated that the hydrophobic or hydrophilic nature of the carbon source had significant influence on the cell surface hydrophobicity. Although the results differed for some individual yeast strains, the generalization can be made that there is the correlation between the best hydrocarbon and phenol degradation and corresponding cell wall properties of the yeast examined.

Yeasts isolated from plant-associated beetles and other insects: seven novelCandidaspecies nearCandida albicans

Yeasts related to Candida albicans were isolated from the digestive tracts of beetles in eight families and various orders of insects such as earwigs, crickets, and roaches, most of which were caught at light traps or in a few cases directly from plant materials. Based on comparisons of DNA sequences and other taxonomic characteristics, a total of 41 isolates were identified as Candida orthopsilosis, Candida pseudorhagii, Candida maltosa, Candida parapsilosis, Candida tropicalis, Candida neerlandica, Lodderomyces elongisporus, and seven new Candida species. The new species and type strains are designated as Candida gigantensis NRRL Y-27736T, Candida bohiensis NRRL Y-27737T, Candida alai NRRL Y-27739T, Candida buenavistaensis NRRL Y-27734T, Candida frijolesensis NRRL Y-48060T, Candida labiduridarum NRRL Y-27940T, and Candida tetrigidarum NRRL Y-48142T. A phylogeny based on SSU and LSU rRNA gene sequences indicated that most of the new species were closely related to members of the C. albicans/L. elongisporus clade, such as C. albicans, Candida dulbliniensis, C. neerlandica, Candida chauliodes, and Candida corydali. Candida alai was placed near this clade, but no closely related sister taxon was identified. The ecology of the insect-associated yeasts is discussed and compared with the results from other studies.

Characterisation of Lactobacillus rhamnosus VT1 and its effect on the growth of Candida maltosa YP1

The combined effect of initial amount of 18 h <i>L. rhamnosus</i> VT1 inoculum and incubation temperature on the growth of <i>Candida maltosa</i> YP1, an oxidative food spoilage yeast strain, was primarily modelled and studied by standard response surface methodology. This study resulted in the following linear regression equations characterising lag time and growth rate of <i>C. maltosa</i> YP1 in milk in competition with the potentially protective lactobacillus strain. Lag-phase of <i>C. maltosa</i> was strongly influenced by the amount of lactobacillus inoculum (<i>V</i><sub>0</sub>) and incubation temperature (1/<i>T</i>). The synergic effect of both these factors was also evident as results from the equation lag = –33.50 + 186.38 × <i>V</i><sub>0</sub> × 1/<i>T</i> + 512.27 × 1/<i>T</i> – 5.511 × <i>V</i><sub>0</sub> (<i>R</i><sup>2</sup><sub>(λ)</sub> = 0.849). The growth rate was sufficiently described by the linear relation: <i>Gr</i><sub>Cm</sub> = –0.00046 + 0.0033 × <i>T</i> – 0.0016 × <i>V</i><sub>0 (<i>R</i><sup>2</sup><sub>(Gr)</sub> = 0.847). On the basis of these equations, the mutual microbial interactions and the potential application of the lactobacillus strains to food protection are discussed.

Yeast and bacteria cell hydrophobicity and hydrocarbon biodegradation in the presence of natural surfactants: Rhamnolipides and saponins

This study concerns the relation between hydrocarbon biodegradation in the presence of natural surfactants and cell hydrophobicity resulting from the use of these surfactants. The relative capabilities of two bacterial strains ( Pseudomonas aeruginosa and Bacillus subtilis) and two yeast strains ( Candida maltosa, Yarrowia lipolytica) were investigated. The selected microorganisms were tested separately and in combination in order to achieve the optimal degrading performance. The surface cell hydrophobicity of microorganisms and the degree of hydrocarbon biodegradation were measured. The microbial adhesion to the hydrocarbon (MATH) test was used to denote the surface cell hydrophobicity of the microbial species. The results indicate the correlation between the modification of the surface cell and the degree of hydrocarbon biodegradation; however results for bacteria differ from that obtained for yeast strains. Saponins, as the surfactant, was more effective than rhamnolipides during hydrocarbon biodegradation, though the concentration of this surfactant has no significant influence on the surface cell hydrophobicity.