Candidum Strains Research Articles

Matrine-producing endophytic fungus Galactomyces candidum TRP-7: screening, identification, and fermentation conditions optimization for Matrine production.

Matrine (MA) is an alkaloid extracted from the root of genus Sophora with various pharmacological activities. Production of MA by endophytic fungi offers an alternative challenge to reduce the massive consumption to meet the increasing demand of MA. In the current study, the positive strains with MA producing ability were screened from endophytic fungal isolated from the root of Sophora tonkinensis Gagnep. Chromatographic analyses verified the identity of the produced MA. Among these fungi, Galactomyces candidum strain TRP-7 was the most valuable strain for MA production with the initial yield 8.26mg L-1. The MA production was efficiently maximized up to 17.57mg L-1 of fermentation broth, after optimization of eight process parameters using Plackett-Burman and Box-Behnken designs. The statistical optimization resulted in a 1.127 times increase in MA production as compared to the initial yield of TRP-7. This is the first report to isolate endophytic fungi with MA-producing activity from S. tonkinensis Gagnep., and to identify an endophytic fungus G. candidum TRP-7 as a new promising start strain for a higher MA yield.

Identification of novel totiviruses from the ascomycetous fungus Geotrichum candidum.

Mycoviruses are widely distributed across the kingdom Fungi, including ascomycetous yeast strains of the class Saccharomycetes. Geotrichum candidum is an important fungal pathogen belonging to Saccharomycetes and has a diverse host range. Here, we report the characterization of four new classical totiviruses from two distinct Geotrichum candidum strains from Pakistan. The four identified viruses were tentatively named "Geotrichum candidum totivirus 1, 2, 3a, and 3b" (GcTV1-3b). The complete dsRNA genomes of the identified totiviruses are 4621, 4592, 4576, and 4576 bp in length, respectively. All totivirus genomes have two open reading frames, encoding a capsid protein (CP) and an RNA-dependent RNA polymerase (RdRP), respectively. The downstream RdRP domain is assumed to be expressed as a CP-RdRP fusion product via -1 frameshifting mediated by a heptameric slippery site. Sequence comparisons and phylogenetic analysis showed that each of the discovered viruses belongs to a new species of the genus Totivirus in the family Totiviridae, with GcTV1 and GcTV3 (a and b strains) clustering in one subgroup and GcTV2 in another subgroup.

ASSESSMENT OF PAINT-PIGMENT DEGRADING MICROORGANISMS FROM PAINT INDUSTRIES EFFLUENT-CONTAMINATED SITES IN ABA, SOUTH-EAST NIGERIA

The potential of microorganisms isolated from paint industry effluent-polluted soils to degrade the constituents of the effluents and contaminant removal efficiency after the remediation period were evaluated. Samples were collected from six different paint industries in Aba. Samples from the various paint industries reveals sample F showed the highest bacterial plate counts of 6.21±0.20 x 104cfu/g while samples B and D had the least bacterial counts of 1.30±0.20 x 104cfu/g and 1.30±0.31 x 104cfu/g respectively. The fungal counts of the polluted soils indicates sample D as having the highest count of 2.30±0.24 x 104cfu/g while sample A had the least count of 1.00±0.30 x104cfu/g. Total Paint Utilizing Fungal (TPUF) counts ranges from 1.23±0.02 x 104cfu/g to 3.45±0.10 x 104cfu/g and showed a significant difference between sample C and the control (p<0.05). The bacterial isolates from the contaminated soil include Pseudomonas spp., Escherichia coli, Citrobacter spp., Klebsiella spp., Proteus spp., Enterobacter spp., Providencia rettgeri, Shigella flexneri, Staphylococcus spp., Streptococcus spp. and Enterococcus spp. while the fungal isolates include Saccharomyces cerevisiae, Rhodotorula species, Rhizopus species, Aspergillus niger, Aspergillus flavus and Penicillum notatum. The counts of actual paint utilizing fungi were relatively lower than the heterotrophic groups. The paint degrading microorganisms isolated from the paint industry effluent polluted soils include paint effluent bacterial degraders: Pseudomonas spp. (33.3%), Escherichia coli(33.3%),, Citrobacter spp. (25%), Klebsiella spp.(25%), Proteus spp.(25%), Enterobacter spp.(12.5%). and Providencia rettgeri(12.5%), While the fungal paint effluent degraders include Geotrichum candidum(33.3%), Pichia kudriavzevii(33.3%), Fusarium sp.(25%), Aspergillus niger(25%), Penicillium funiculosum(25%) and Mucor sp.(12.5%). Geotrichum candidum strain GAD1 (MN63874.1) and Pichia kudriavzevii strain (MK811096.1) showed highest degrees of growth indicated by high turbidities during the screening test. This study showed that majority of the Indigenous organisms has the ability to utilize paints as their sole carbon source hence are the major bioremediating agents in the sampling areas.

Molecular Genetic Analysis with Microsatellite-like Loci Reveals Specific Dairy-Associated and Environmental Populations of the Yeast Geotrichum candidum.

Geotrichum candidum is an environmental yeast, also found as part of the cheese surface microbiota, where it is important in the ripening of many traditional cheeses, such as Camembert. We have previously developed a Multi Locus Sequence Typing (MLST) scheme, which differentiated five clades, of which one contained only environmental isolates, two were composed almost entirely of dairy isolates, and two others contained a mixture of dairy, environmental, and miscellaneous food isolates. In order to provide a simple method to uniquely type G. candidum strains, and in addition to permit investigation of the population structure at a fine level, we describe here a molecular analysis using a set of twelve highly discriminating microsatellite-like markers. The present study consolidates the previously suggested division between dairy and environmental strains, and in addition distinguishes a specifically European group of environmental strains. This analysis permitted the discrimination of 72 genotypes from the collection of 80 isolates, while retaining the underlying meaningful phylogenetic relation between groups of strains.

Phenotypic and Genetic Characterization of the Cheese Ripening Yeast Geotrichum candidum.

The yeast Geotrichum candidum (teleomorph Galactomyces candidus) is inoculated onto mold- and smear-ripened cheeses and plays several roles during cheese ripening. Its ability to metabolize proteins, lipids, and organic acids enables its growth on the cheese surface and promotes the development of organoleptic properties. Recent multilocus sequence typing (MLST) and phylogenetic analyses of G. candidum isolates revealed substantial genetic diversity, which may explain its strain-dependant technological capabilities. Here, we aimed to shed light on the phenotypic and genetic diversity among eight G. candidum and three Galactomyces spp. strains of environmental and dairy origin. Phenotypic tests such as carbon assimilation profiles, the ability to grow at 35°C and morphological traits on agar plates allowed us to discriminate G. candidum from Galactomyces spp. The genomes of these isolates were sequenced and assembled; whole genome comparison clustered the G. candidum strains into three subgroups and provided a reliable reference for MLST scheme optimization. Using the whole genome sequence as a reference, we optimized an MLST scheme using six loci that were proposed in two previous MLST schemes. This new MLST scheme allowed us to identify 15 sequence types (STs) out of 41 strains and revealed three major complexes named GeoA, GeoB, and GeoC. The population structure of these 41 strains was evaluated with STRUCTURE and a NeighborNet analysis of the combined six loci, which revealed recombination events between and within the complexes. These results hint that the allele variation conferring the different STs arose from recombination events. Recombination occurred for the six housekeeping genes studied, but most likely occurred throughout the genome. These recombination events may have induced an adaptive divergence between the wild strains and the cheesemaking strains, as observed for other cheese ripening fungi. Further comparative genomic studies are needed to confirm this phenomenon in G. candidum. In conclusion, the draft assembly of 11 G. candidum/Galactomyces spp. genomes allowed us to optimize a genotyping MLST scheme and, combined with the assessment of their ability to grow under different conditions, provides a reliable tool to cluster and eventually improves the selection of G. candidum strains.

Retraction for Polev et al., "Draft Genome Sequence of Geotrichum candidum Strain 3C".

Volume 2, no. 5, e00956-14, 2014, [https://doi.org/10.1128/genomeA.00956-14][1]. We retract this article. The Geotrichum candidum strain 3C was initially identified and classified in the early 1970s (N. A. Rodionova, N. A. Tiunova, R. V. Feniksova, T. I. Kudriashova, and L. I. Martinovich, Dokl Akad

Purification, Characterization and Thermodynamic Assessment of an Alkaline Protease by Geotrichum Candidum of Dairy Origin.

BackgroundAlkaline proteases is the important group of enzymes having numerous industrial applications including dairy food formulations.ObjectivesThe current study deals with the purification and characterization of an alkaline serine protease produced by Geotrichum candidum QAUGC01, isolated from indigenous fermented milk product, Dahi.Material and MethodsIn total twelve G. candidum strains were screened for their proteolytic activity by using standard protease assay. The protease production from G. candidum QAUGC01 was optimized by varying physio-chemical conditions. The protease was purified by using two-step method: ammonium sulfate precipitation and gel filtration chromatography. Protease was further characterized by studying various parameter like temperature, pH, modulators, metal ions and organic solvent. A thermodynamic study was also carried out to explore the half-life of protease.ResultsThe G. candidum grew profusely at 25 °C and at an initial pH of 4.0 for 72 h of incubation producing 26.21 U/ml maximum extracellular protease. Protease revealed that Vmax and Km was 26.25 U.ml-1.min-1 and 0.05 mg.mL-1, respectively using casein as substrate. The enzyme was stable at a temperature range (25–45 °C) and pH (8–9). Residual enzyme activity was strongly inhibited in the presence of PMSF (7.5%). The protease could hydrolyze proteinaceous substrates, casein (98%) and BSA (95%). The thermodynamic studies explored that the half-life of the enzyme that was 106.62 min, 38.72 min and 15.71 min at 50, 60 and 70 °C, respectively.ConclusionsPurified protease from G. candidum GCQAU01 is an ideal candidate for industrial application.

Phenotypic and genotypic identification of yeasts isolated from some dairy products

Yeast classification is traditionally based on their physiological and biochemical profiles. Recently, molecular methods have been successfully applied to yeast strain typing and identification. The aim of this paper was to characterize four yeast strains isolated from dairy products by classical and molecular methods. The preliminary examination involved macroscopic appearances of colonies on solid media and microscopic feature of the cells. Physiological characterization was mainly performed by assessing the ability to use certain sugars semi-anaerobically, the ability to use organic compounds as sole carbon source for aerobic growth, urea hydrolysis, growth at high concentrations of glucose and the ability to growth at non-optimal temperatures (37°C and 42°C). From results obtained it could be stated that, although there were some variations in biochemical patterns all tested yeasts were classified either as S. cerevisiae or and G. candidum with 95 – 99 % of probability. For molecular identification only three specific primer pairs and one universal primer were used. The identification was carried out based on ITS 1 partial sequence, 5.8 S rRNA gene and ITS 2 complete sequence and large subunit rRNA gene sequence analysis. The results obtained showed that the product of S. cerevisiae scored 600 bp in lan (1and 2) using 5.8 S rRNA gene with primer ITS and NL2, while G. candidum scored 600 bp in lan (3and 4) using 18S rDNA gene with primer (18S ITS1 – 28S ITS 2). However, the sequence analysis of the four identified yeast strains was submitted to Genebank in the NCBI database. They have been accepted to be deposited and released in Genebank under four new accession numbers, actually KY441458, MF380234 for S. cerevisiae and MF383376, MF383368 for G. candidum strains. In conclusion, Strains were locally isolated from Egyptian resources to increase the additive value of the Egyptian microbial wealth.

Regioselectivity and fatty acid specificity of crude lipase extracts from Pseudozyma tsukubaensis, Geotrichum candidum, and Candida rugosa

Microbial lipases are of particular interest for biotechnological applications because of their high specificity and their ability to perform reactions at room temperature. Here are characterized extracellular and cell‐bound crude lipase extracts from the yeasts Pseudozyma tsukubaensis CBS 422.96, Candida rugosa CBS 5213, and Geotrichum candidum NRRL Y‐552. Enzyme preparations were optimally active at neutral pH and ambient temperature, and displayed different substrate specificities. Unlike P. tsukubaensis and C. rugosa extracts, crude lipases from G. candidum were unable to hydrolyze ethyl esters of saturated fatty acids (C8:0–C18:0). The activity of extracts from P. tsukubaensis was maximal for the octyl chain and then decreases as the acyl chain was lengthened, while cell‐bound lipases from C. rugosa hydrolyzed any saturated fatty acid ethyl esters from C8:0 to C18:0. Preparations from C. rugosa and P. tsukubaensis displayed a sn‐1,3‐regioselectivity on triolein, while cell‐bound lipases from G. candidum were non‐regioselective. The extracellular crude lipases from G. candidum exhibited a small preference for the internal position both on triolein and on six edible oils, releasing a high proportion of DAG‐1,3 (∼50%) compared to DAG‐1,2(2,3). To the contrary, extracts from P. tsukubaensis and C. rugosa catalyzed the formation of almost 100% DAG‐1,2(2,3) from oils.Practical applications: Oils with a high DAG‐1,3 content have attracted considerable attention as healthful foods capable of lowering plasmatic level of TAG. Our results suggest that the crude enzymatic extracts from the wild‐type, non‐genetically modified G. candidum strain might be particularly well adapted for partial hydrolysis of oils to produce such nutraceutical diacylglycerols. In non‐optimized conditions, about 50/50% of DAG‐1,2(2,3)/DAG‐1,3 was already obtained, especially for rapeseed oil.This lab‐scale study shows the potential and substrate specificities of various microbial crude lipase extracts for hydrolysis of edible oils

Specific populations of the yeast Geotrichum candidum revealed by molecular typing.

Geotrichum candidum is a ubiquitous yeast and an essential component in the production of many soft cheeses. We developed a multilocus sequence typing (MLST) scheme with five retained loci (NUP116, URA1, URA3, SAPT4 and PLB3) which were sufficiently divergent to distinguish 40 sequence types (STs) among the 67 G. candidum strains tested. Phylogenetic analyses defined five main clades; one clade was restricted to environmental isolates, three other clades included distinct environmental isolates and dairy strains, while the fifth clade comprised 34 strains (13 STs), among which all but two were isolated from milk, cheese or the dairy environment. These findings suggest an adaptation to the dairy ecosystems by a group of specialized European G. candidum strains. In addition, we developed a polymerase chain reaction inter-long terminal repeat scheme, a fast and reproducible random amplification of polymorphic DNA-like method for G. candidum, to type the closely related dairy strains, which could not be distinguished by MLST. Overall, our findings distinguished two types of dairy strains, one forming a homogeneous group with little genetic diversity, and the other more closely related to environmental isolates. Neither regional nor cheese specificity was observed in the dairy G. candidum strains analysed. This present study sheds light on the genetic diversity of both dairy and environmental strains of G. candidum and thus extends previous characterizations that have focused on the cheese isolates of this species. Copyright © 2016 John Wiley & Sons, Ltd.

Biodiversity Evaluation of Geotrichum candidum Link. Is Arthrosporic Nucleus Number in Geotrichum candidum related to the Fungus Biodiversity?

Abstract Geotrichum candidum species exhibits properties of both moulds and yeasts and its affiliation to one of the groups has been intensively discussed. It is because this filamentous microscopic fungus is displaying substantial morphological variability and wide phenotypic diversity. The present study assesses the variability of arthrosporic nucleus number of twelve isolates of G. candidum originating from artisanal manufacturing and ripened traditional Slovak cheeses. Results showed that arthrospores of the studied isolates contained on average 1.5 ± 0.7 (on the Gorodkova medium) and 1.5 ± 0.6 (on the McClary medium) Hoechst 33258-stained nuclei (range 1–4 nuclei on both agars) after a 7-day cultivation at 25°C. Majority of arthrospores comprised one nucleus, irrespective to the used nutrient-limited medium. Generally, a higher relative nucleus number per arthrospore was exhibited in yeast-like isolates with microscopic structure composed predominantly of spores, while it was lower in vegetative hyphae. These isolates originated from ewe’s lump cheese. Our study reveals that the arthrosporic nucleus number of the G. candidum strains is closely related to morphotype and origin of this yeast.

English

Four batches of Armada semi-hard goat cheese were elaborated from pasteurized milk inoculated with a natural starter culture, constituted of two lactococci strains, combined with a Geotrichum candidum strain. The four G. candidum strains tested as co-starter were selected for their proteolytic and lipolytic activities. The effects of an autochthonous starter on physico-chemical, microbiological and sensorial characteristics during the ripening of this cheese were evaluated. The depth of proteolysis was very low, which confirms the presence of low-level aminopeptidase activity. Fungal population was involved in lipolysis. The cheeses elaborated with G. candidum strains developed a desirable flavour characteristic of goat cheese and a creamy texture. Cheeses from batch I (that included the strain of G. candidum with high lipolytic activity and low proteolytic activity) presented a hardness profile that differed from the others, as it was the batch with the highest scores at thirty days of ripening and was even the best evaluated at the end of ripening because of their odour, fresh balanced pleasant taste and creamy smooth texture. Key words: Cheese, starter culture, Geotrichum candidum, lactic acid bacteria.

Enzymatic and molecular characteristics ofGeotrichum candidumstrains as a starter culture for malting

Geotrichum candidum yeasts are proposed as a starter culture during malting. They have a double positive effect on the process. They eliminate the fungal pathogenic microflora and improve the technological properties of the finished product, malt. Among published research little or no information can be found considering the biosynthesis of hydrolytic enzymes. Most of the data is related to the production of lipases, proteases and cellulases. This paper examines the enzymology of a number of G. candidum strains. The main focus within the evaluation process was placed on whole cell barley grain cultivation. Hydrolase, which is present in cell wall degradation, was found at a satisfactory level. All tested strains produced both β-1,3-glucanases and β-1,4-glucanases capable of hydrolysing barley β-glucan and reducing the amount of this polysaccharide in the wort. Molecular analysis of the tested strains with the use of restriction fragment length polymorphism–polymerase chain reaction and randomly amplified polymorphic DNA confirmed not only the species affiliation, but also the genetic similarity between the tested strains. Copyright © 2014 The Institute of Brewing & Distilling

Mycelium-bound lipase from a locally isolated strain of Geotrichum candidum.

Mycelium-bound lipase (MBL), from a locally isolated Geotrichum candidum strain, was produced and characterized as a natural immobilized lipase. A time course study of its lipolytic activity in 1 L liquid broth revealed the maximum MBL activity at 4 h for mycelium cells harvested after 54 h. The yield and specific activity of MBL were 3.87 g/L dry weight and 508.33 U/g protein, respectively, while less than 0.2 U/mL lipase activity was detected in the culture supernatant. Prolonged incubation caused release of the bound lipase into the growth medium. The growth pattern of G. candidum, and production and properties of MBL were not affected by the scale. The stability of mycelia harboring lipase (MBL), harvested and lyophilized after 54 h, studied at 4 °C depicted a loss of 4.3% and 30% in MBL activity after 1 and 8 months, while the activity of free lipase was totally lost after 14 days of storage. The MBL from G. candidum displayed high substrate selectivity for unsaturated fatty acids containing a cis-9 double bond, even in crude form. This unique specificity of MBL could be a direct, simple and inexpensive way in the fats and oil industry for the selective hydrolysis or transesterification of cis-9 fatty acid residues in natural triacylglycerols.

Genetic diversity of dairy Geotrichum candidum strains revealed by multilocus sequence typing

The introduction of multilocus sequence typing (MLST) for strain characterization provided the first sequence-based approach for genotyping many fungi, leading to reproducible, reliable, and exchangeable data. A MLST scheme based on the analysis of six housekeeping genes was developed for genotyping Geotrichum candidum. The scheme was first developed using 18 isolates for which the complete sequences of the alanyl-tRNA synthetase (ALA1), pyruvate kinase (CDC19), acetyl-coA acetyltransferase (ERG10), glutaminyl-tRNA synthase (GLN4), phosphoglucoisomerase (PGI1), and phosphoglucomutase (PGM2) housekeeping genes were determined. Multiple sequence alignments of these genes were used to define a set of loci showing, as closely as possible, the same phylogenetic resolution level as complete gene sequences. This scheme was subsequently validated with 22 additional isolates from dairy and non-dairy sources. Overall, 58 polymorphic sites were indexed among 3,009 nucleotides analyzed. Depending on the loci, four to eight alleles were detected, generating 17 different sequence types, of which ten were represented by a single strain. MLST analysis suggested a predominantly clonal population for the 40 G. candidum isolates. Phylogenetic analysis of the concatenated sequences revealed a distantly related group of four isolates. Interestingly, this group diverged with respect to internal transcribed spacers 1 (ITS1), 5.8S, and ITS2 analysis. The reproducibility of the MLST approach was compared to random amplification of microsatellites by PCR (RAM-PCR), a gel profiling method previously proposed for G. candidum strain typing. Our results found MLST differentiation to be more efficient than RAM-PCR, and MLST also offered a non-ambiguous, unique language, permitting data exchange and evolutionary inference.

Thermal Alkaline Method to Prepare Geotrichuam Candidum Protein Foaming Agent

Geotrichum Candidum strain numbered 2.0498 was used as raw material. The Geotrichum Candidum thallus were collected through inoculation and shaking cultivation. Thermal alkaline method was applied for hydrolyzing Geotrichum Candidum mycoprotein to prepare protein foaming agent. The effect of bacteria concentration, Ca(OH)2mass concentration, hydrolysis temperature and hydrolysis time on foam expansion were studied. The optimization strategy was single factor test and subsequent response surface analysis based on Box-Behnken design. The results showed that the optimized condition were a bacteria concentration of 5.4%(w/v) and a Ca(OH)2mass concentration of 1.5%(w/v), at a hydrolysis temperature of 95°C for 4.1 h. Under these optimal conditions, the foam expansion was 28.1. Compared with the model theory prediction, the relative error was 0.46%. At the same time, a multiple quadratic regression equation between Geotrichum Candidum mycoprotein foam expansion and impact factors was setted up and it played an important role in predicting the foam expansion.

Technological characterization of Geotrichum candidum strains isolated from a traditional Spanish goats’ milk cheese

Forty-one strains of Geotrichum candidum isolated from Armada cheese, Sobado variety, were screened for their enzymatic activities, including proteolytic and lipolytic activities and aminopeptidase activity. The highest extracellular proteolytic activity was detected for 8 strains with values ranging between 2.086 and 4.685 mM Gly L−1 of milk. Extracellular lipolytic activity was high for all but one of the G. candidum strains, with values ranging between 67 and 131 μmol oleic mL−1. Cell-bound lipase activity showed values which were considerably lower than those for extracellular activity, ranging between 32.50 and 42.50 μmol oleic mL−1 and falling below 20 μmol oleic mL−1 in 28 strains. Aminopeptidase activity was not very high in the cell-free extract (CFE) of any of the strains, showing the highest values toward the substrate Lys-p-nitroanilide, with levels of activity ranging between 6.12 and 10.05 UE mg−1 protein in 8 strains. In accordance with the results obtained, four G. candidum strains were selected as co-cultures in order to study their role in the ripening of a semi-hard goat’s milk cheese.

Ribosomal DNA polymorphisms in the yeast Geotrichum candidum

The dimorphic yeast Geotrichum candidum (teleomorph: Galactomyces candidus) is commonly used to inoculate washed-rind and bloomy-rind cheeses. However, little is known about the phylogenetic lineage of this microorganism. We have sequenced the complete 18S, 5.8S, 26S ribosomal RNA genes and their internal transcribed spacers (ITS1) and ITS2 regions (5126 nucleotides) from 18 G. candidum strains from various environmental niches, with a focus on dairy strains. Multiple sequence alignments revealed the presence of 60 polymorphic sites, which is generally unusual for ribosomal DNA (rDNA) within a given species because of the concerted evolution mechanism. This mechanism drives genetic homogenization to prevent the divergent evolution of rDNA copies within individuals. While the polymorphisms observed were mainly substitutions, one insertion/deletion (indel) polymorphism was detected in ITS1. No polymorphic sites were detected downstream from this indel site, that is, in 5.8S and ITS2. More surprisingly, many sequence electrophoregrams generated during the sequencing of the rDNA had dual peaks, suggesting that many individuals exhibited intragenomic rDNA variability. The ITS1–5.8S–ITS2 regions of four strains were cloned. The sequence analysis of 68 clones revealed 32 different ITS1–5.8S–ITS2 variants within these four strains. Depending on the strain, from four to twelve variants were detected, indicating that multiple rDNA copies were present in the genomes of these G. candidum strains. These results contribute to the debate concerning the use of the ITS region for barcoding fungi and suggest that community profiling techniques based on rDNA should be used with caution.

Selection of non-conventional yeasts and their use in immobilized form for the bioremediation of olive oil mill wastewaters

The yeast population dynamics in olive wastewaters (OMW), sampled in five mills from Salento (Apulia, Southern Italy), were investigated. Three hundred yeasts were isolated in five industrial mills and identified by molecular analysis. Strains belonging to Geotrichum, Saccharomyces, Pichia, Rhodotorula and Candida were detected. Five G. candidum strains were able to grow in OMW as the sole carbon source and to reduce phenolics, chemical oxygen demand (COD) and antimicrobial compounds. One G. candidum isolate was selected for whole-cell immobilization in calcium alginate gel. The COD and phenolic reduction obtained with immobilized cells showed a 2.2- and 2-fold increase compared to the removal obtained with free cells, respectively. The immobilization system enhanced yeast oxidative activity by avoiding the presence of microbial protease in treated OMW. To our knowledge, this is the first report on G. candidum whole-cell immobilization for OMW bioremediation.

Levels of cystathionine γ lyase production by Geotrichum candidum in synthetic media and correlation with the presence of sulphur flavours in cheese

Geotrichum candidum is a cheese-ripening agent with the potential to produce sulphur flavour compounds in soft cheeses. We aimed to develop an alternative test for predicting the aromatic (sulphur flavours) potential of G. candidum strains in soft cheese. Twelve strains of G. candidum with different levels of demethiolase activity (determined by a chemical method) in YEL–met (yeast extract, lactate methionine) medium were studied. We investigated cgl (cystathionine gamma lyase) gene expression after culture in three media – YEL–met, casamino acid and curd media – and then carried out sensory analysis on a Camembert cheese matrix. We found no correlation between demethiolase activity in vitro and cgl gene expression. Sensory analysis (detection of sulphur flavours) identified different aromatic profiles linked to cgl expression, but not to demethiolase activity. The RT-PCR technique described here is potentially useful for predicting the tendency of a given strain of G. candidum to develop sulphur flavours in cheese matrix. This is the first demonstration that an in vitro molecular approach could be used as a predictive test for evaluating the potential of G. candidum strains to generate sulphur compounds in situ (Camembert cheese matrix).