RESUMEN
Temperature fluctuation commonly occurs in the cold chain leading to complete or partial thawing and refreezing of frozen products resulting in a multifrozen product. Such oscillation of temperature could cause significant quality reduction compared to single frozen products. This study was designed to differentiate frozen Atlantic salmon fillets based on the level of temperature fluctuation. Near-infrared spectroscopy (NIRS) coupled with chemometrics was used to classify the frozen fillets stored at no fluctuation (NF), low fluctuation (LF), high fluctuation (HF), and very high fluctuation (VF) temperature. Using spectral profiles obtained at both frozen and thawed states, fillets were classified based on the level of temperature fluctuation by partial least squares discriminant analysis (PLS-DA). The thawed samples showed better classification accuracy (71%) than frozen samples (66%) in a four-class model. Considering the small variation within the first two (NF, LF) and the last two (HF, VF) groups, a two-class classification model was developed using thawed samples, and the obtained model correctly classified the two groups ([NF, LF] and [HF, VF]) with 100 % classification accuracy. Protein- and water-related changes were found important to distinguish the fillets. Based on these findings, the four-class prediction model is found insufficient to be used for nondestructive determination of temperature history of frozen fillets. However, the two-class prediction model with further external validation can be applied to determine the level of temperature fluctuation particularly using fillets scanned at thawed state. PRACTICAL APPLICATION: NIR spectroscopy can be used to evaluate the degree of temperature fluctuation and thus related quality loss throughout the logistics of frozen Atlantic salmon fillets. Researchers, food control authorities, and the retail industry could be the primary beneficiaries of this research output.
Asunto(s)
Salmo salar , Espectroscopía Infrarroja Corta , Animales , Estudios de Factibilidad , Alimentos Marinos/análisis , TemperaturaRESUMEN
Bioethanol fermentations expose yeasts to a new, complex and challenging fermentation medium with specific inhibitors and sugar mixtures depending on the type of carbon source. It is, therefore, suggested that the natural diversity of yeasts should be further exploited in order to find yeasts with good ethanol yield in stressed fermentation media. In this study, we screened more than 50 yeast isolates of which we selected five isolates with promising features. The species Candida bombi, Wickerhamomyces anomalus and Torulaspora delbrueckii showed better osmo- and hydroxymethylfurfural tolerance than Saccharomyces cerevisiae. However, S. cerevisiae isolates had the highest ethanol yield in fermentation experiments mimicking high gravity fermentations (25 % glucose) and artificial lignocellulose hydrolysates (with a myriad of inhibitors). Interestingly, among two tested S. cerevisiae strains, a wild strain isolated from an oak tree performed better than Ethanol Red, a S. cerevisiae strain which is currently commonly used in industrial bioethanol fermentations. Additionally, a W. anomalus strain isolated from sugar beet thick juice was found to have a comparable ethanol yield, but needed longer fermentation time. Other non-Saccharomyces yeasts yielded lower ethanol amounts.
Asunto(s)
Biocombustibles/microbiología , Etanol/metabolismo , Saccharomyces cerevisiae/metabolismo , Candida/metabolismo , Fermentación , Lignina/metabolismo , Fenotipo , Saccharomycetales/metabolismoRESUMEN
Saccharomyces cerevisiae is the organism of choice for many food and beverage fermentations because it thrives in high-sugar and high-ethanol conditions. However, the conditions encountered in bioethanol fermentation pose specific challenges, including extremely high sugar and ethanol concentrations, high temperature, and the presence of specific toxic compounds. It is generally considered that exploring the natural biodiversity of Saccharomyces strains may be an interesting route to find superior bioethanol strains and may also improve our understanding of the challenges faced by yeast cells during bioethanol fermentation. In this study, we phenotypically evaluated a large collection of diverse Saccharomyces strains on six selective traits relevant for bioethanol production with increasing stress intensity. Our results demonstrate a remarkably large phenotypic diversity among different Saccharomyces species and among S. cerevisiae strains from different origins. Currently applied bioethanol strains showed a high tolerance to many of these relevant traits, but several other natural and industrial S. cerevisiae strains outcompeted the bioethanol strains for specific traits. These multitolerant strains performed well in fermentation experiments mimicking industrial bioethanol production. Together, our results illustrate the potential of phenotyping the natural biodiversity of yeasts to find superior industrial strains that may be used in bioethanol production or can be used as a basis for further strain improvement through genetic engineering, experimental evolution, or breeding. Additionally, our study provides a basis for new insights into the relationships between tolerance to different stressors.
Asunto(s)
Etanol/metabolismo , Etanol/toxicidad , Microbiología Industrial/métodos , Saccharomyces cerevisiae/efectos de los fármacos , Saccharomyces cerevisiae/crecimiento & desarrollo , Biodiversidad , Tolerancia a Medicamentos , Saccharomyces cerevisiae/metabolismoRESUMEN
Although the number of studies investigating mycorrhizal associations in orchids has increased in recent years, the fungal communities associating with orchids and how they differ between species and sites remain unclear. Recent research has indicated that individual orchid plants may associate with several fungi concurrently, implying that to study mycorrhizal associations in orchids the fungal community should be assessed, rather than the presence of individual dominant fungal species or strains. High-throughput sequencing methods, such as 454 pyrosequencing, are increasingly used as the primary tool for such analyses. However, many studies combine universal primers from previous phylogenetic or ecological studies to generate amplicons suitable for 454 pyrosequencing without first critically evaluating their performance, potentially resulting in biased fungal community descriptions. Here, following in silico primer analysis we evaluated the performance of different combinations of existing PCR primers to characterize orchid mycorrhizal communities using 454 pyrosequencing by analysis of both an artificially assembled community of mycorrhizal fungi isolated from diverse orchid species and root samples from three different orchid species (Anacamptis morio, Ophrys tenthredinifera and Serapias lingua). Our results indicate that primer pairs ITS3/ITS4OF and ITS86F/ITS4, targeting the internal transcribed spacer-2 (ITS-2) region, outperformed other tested primer pairs in terms of number of reads, number of operational taxonomic units recovered from the artificial community and number of different orchid mycorrhizal associating families detected in the orchid samples. Additionally, we show the complementary specificity of both primer pairs, making them highly suitable for tandem use when studying the diversity of orchid mycorrhizal communities.
Asunto(s)
Biota , Cartilla de ADN/genética , Micorrizas/clasificación , Micorrizas/genética , Orchidaceae/microbiología , Análisis de Secuencia de ADN/métodos , Análisis por Conglomerados , ADN de Hongos/química , ADN de Hongos/genética , ADN Espaciador Ribosómico/química , ADN Espaciador Ribosómico/genética , Datos de Secuencia Molecular , FilogeniaRESUMEN
A soil sterilization-reinoculation approach was used to manipulate soil microbial diversity and to assess the effect of the diversity of the ammonia-oxidizing bacteria (AOB) on the recovery of the nitrifying community to metal stress (zinc). Gamma-irradiated soil was inoculated with 13 different combinations of up to 22 different soils collected worldwide to create varying degrees of AOB diversity. Two months after inoculation, AOB amoA DGGE based diversity (weighted richness) varied more than 10-fold among the 13 treatments, the largest value observed where the number of inocula had been largest. Subsequently, the 13 treatments were either or not amended with ZnCl2. Initially, Zn amendment completely inhibited nitrification. After 6 months of Zn exposure, recovery of the potential nitrification activity in the Zn amended soils ranged from <10 % to >100 % of the potential nitrification activity in the corresponding non-amended soils. This recovery was neither related to DGGE-based indices of AOB diversity nor to the AOB abundance assessed 2 months after inoculation (p > 0.05). However, recovery was significantly related (r = 0.75) to the potential nitrification rate before Zn amendment and only weakly to the number of soil inocula used in the treatments (r = 0.46). The lack of clear effects of AOB diversity on recovery may be related to an inherently sufficient diversity and functional redundancy of AOB communities in soil. Our data indicate that potential microbial activity can be a significant factor in recovery.
Asunto(s)
Amoníaco/metabolismo , Bacterias/aislamiento & purificación , Bacterias/metabolismo , Biodiversidad , Microbiología del Suelo , Zinc/metabolismo , Bacterias/clasificación , Bacterias/genética , Ecosistema , Nitrificación , Oxidación-Reducción , Suelo/química , Zinc/análisisRESUMEN
Copper (Cu) containing fungicides have been used for more than one century in Europe on agricultural soils, such as vineyard soils. Total Cu concentrations in such soils can exceed toxicological limits that are commonly derived using artificially spiked soils. This study surveyed Cu toxicity in vineyard soils with reference to soils spiked with CuCl(2). Soil was collected in six established European vineyards. At each site, samples representing a Cu concentration gradient were collected. A control (uncontaminated) soil sampled nearby the vineyard was spiked with CuCl(2). Toxicity was tested using standard ecotoxicity tests: two plant assays (Lycopersicon esculentum Miller (tomato) and Hordeum vulgare L. (barley) growth), one microbial assay (nitrification) and one invertebrate assay (Enchytraeus albidus reproduction). Maximal total Cu concentrations in the vineyard sites ranged 435-690 mg Cu kg(-1), well above the local background (23-105 mg Cu kg(-1)). Toxicity in spiked soils (50% inhibition) was observed at added soil Cu concentrations from 190 to 1039 mg Cu kg(-1) (mean 540 mg Cu kg(-1)) depending on the assay and the site. In contrast, significant adverse effects were only found for three bioassays in vineyard samples of one site and for two bioassays in another site. Biological responses in these cases were more importantly explained by other soil properties than soil Cu. Overall, no Cu toxicity to plants, microbial processes and invertebrates was observed in vineyard soil samples at Cu concentrations well above European Union limits protecting the soil ecosystem.
Asunto(s)
Agricultura , Cobre/toxicidad , Contaminantes del Suelo/toxicidad , Vitis , Animales , Europa (Continente) , Hordeum/efectos de los fármacos , Invertebrados/efectos de los fármacos , Solanum lycopersicum/efectos de los fármacosRESUMEN
The red mud accident of October 4, 2010, in Ajka (Hungary) contaminated a vast area with caustic, saline red mud (pH 12) that contains several toxic trace metals above soil limits. Red mud was characterized and its toxicity for plants was measured to evaluate the soil contamination risks. Red mud radioactivity (e.g., (238)U) is about 10-fold above soil background and previous assessments revealed that radiation risk is limited to indoor radon. The plant toxicity and trace metal availability was tested with mixtures of this red mud and a local noncontaminated soil up to a 16% dry weight fraction. Increasing red mud applications increased soil pH to maximally 8.3 and soil solution EC to 12 dS m(-1). Shoot yield of barley seedlings was affected by 25% at 5% red mud in soil and above. Red mud increased shoot Cu, Cr, Fe, and Ni concentrations; however, none of these exceed toxic limits reported elsewhere. Moreover, NaOH amended reference treatments showed similar yield reductions and similar changes in shoot composition. Foliar diagnostics suggest that Na (>1% in affected plants) is the prime cause of growth effects in red mud and in corresponding NaOH amended soils. Shoot Cd and Pb concentrations decreased by increasing applications or were unaffected. Leaching amended soils (3 pore volumes) did not completely remove the Na injury, likely because soil structure was deteriorated. The foliar composition and the NaOH reference experiment allow concluding that the Na salinity, not the trace metal contamination, is the main concern for this red mud in soil.