Ferulic acid reduced histamine levels in the smoked horsemeat sausage

This study assessed the effect of ferulic acid on the accumulation of histamine in traditional Xinjiang smoked horsemeat sausage. The dynamics of histamine‐producing microorganisms were monitored by PCR‐denaturing gradient gel electrophoresis (DGGE) with specific primer pairs, and histidine and histamine levels were measured by high‐performance liquid chromatography (HPLC). Relative parameters including microbiological growth, pH and moisture content were also evaluated. PCR‐DGGE provided a rapid and convenient method for detecting and identifying histamine‐producing bacteria. The results showed that ferulic acid reduced the histamine concentration and inhibited the growth of histamine‐producing bacteria during fermentation and ripening. Additionally, the inhibitory effect of ferulic acid was stronger than that of the starter culture. Therefore, ferulic acid appears to be a useful additive for manufacturing fermented sausages.     

Batch treatment of liquid fraction of pig slurry by intermittent aeration: process simulation and microbial community analysis

BACKGROUND: Manure treatment in intensive livestock farming is required to reduce the risk of negative environmental impacts by nitrogen disposal. Biological removal through intermittent aeration in a single bioreactor is a suitable method for this purpose. The characteristic operation based on the alternation of oxic/anoxic phases confers these systems with certain particularities in terms of process modelling and of understanding the microbial interactions. RESULTS: The performance of a sequencing batch reactor (SBR) treating raw liquid fraction of pig slurry (LFPS) under loading rates of 0.13 g N L^?1 d^?1 was studied. Three different aeration strategies were applied: (1) constant airflow; (2) dissolved oxygen (DO) set‐point; and (3) DO‐based real‐time control. The comparatively low aeration intensity applied throughout the third strategy resulted in the process being performed mainly via nitrite, implying a reduction on the requirements of organic carbon and oxygen. However, a decrease in the nitrification rate was observed under those conditions. Experimental results were satisfactorily simulated by a mathematical model focused on organic carbon and nitrogen removal. Microbial community structure analysis through denaturing gradient gel electrophoretic profiling of 16S rDNA genes showed that the aeration exerted a strong influence on the dominant microbial populations. The presence of the ammonia‐oxidizing species Nitrosomonas europaea, and of denitrifying bacteria related to Thauera sp. and Ralstonia sp., was detected in the strategy at low DO. CONCLUSION: Dependence of model statement and parameter values on the bioreactor operational patterns and piggery wastewater composition was evidenced. Oxygen limitation was responsible for a significant microbial shift in SBR treating LFPS. Copyright © 2009 Society of Chemical Industry     

Characterization of microbial communities in a fluidized-pellet-bed bioreactor for wastewater treatment

In order to make clear the microbiological characteristics of the fluidized-pellet-bed bioreactor (FPB) which is a newly developed wastewater treatment device to perform coagulation, particle pelletization, biological degradation and solid-liquid separation in a single unit, the method of denaturing gradient gel electrophoresis (DGGE) was applied in this study paying attention to the microbial diversity of the granular sludge. Spread plate method was also used for enumeration of aerobic bacteria in unit weight of granular sludge. As a result, slight difference was found between the total aerobic bacteria at the bottom, middle, and top sections though the dissolved oxygen (DO) concentration decreased from about 3.5 mg/L at the bottom inlet to 0.23 mg/L at the top of the FPB bioreactor. From the DGGE finger printing, 17 common species were identified from all these sections, and certain specific species were also identified from each section. The comparability of the microbial communities in the three sections was 83.1%, indicating a very stable structure of the microbial communities. The 16 S rRNA sequence analysis results revealed that the 18 operational taxonomic units (OTUs) obtained all belong to Eubacteria. Among them 11 are Proteobacteria, 3 are Actinobacteria, 2 are low G + C gram-positive bacteria and the remaining 2 belong to other bacteria branches. The dominant microbial communities are typical aerobes or facultative anaerobes commonly encountered in conventional activated sludge.     

Assessment of the presence and dynamics of fungi in drinking water sources using cultural and molecular methods

A comparison of different isolation techniques and culture media for detection of filamentous fungi and yeasts in the aquatic environment revealed that the use of membrane filtration with the media dichloran rose bengal chloramphenicol (DRBC) optimized fungi detection in terms of abundance and variety in three untreated water sources with very different characteristics (surface water, spring water, and groundwater). The diversity of the fungi population captured by direct DNA extraction of fungi collected by membrane filtration was compared with the isolates obtained after selective growth using different culture media through amplification of the internal transcribed spacer gene and denaturing gradient gel electrophoresis (DGGE). The Czapek-Dox agar, Sabouraud dextrose agar, and DRBC media showed closer similarities to those obtained by the uncultured biomass for the different water sources. Based on these data and the best enumeration results, DRBC is recommended for the assessment of fungi in water sources using culture-based methods. DGGE was also used to monitor temporal variations in the fungal population structure and showed that each water matrix possessed a distinct population profile as well as that changes in the fungal community can be expected in the different matrices throughout the year.     

New monitoring approach for metabolic dynamics in microbial ecosystems using stable-isotope-labeling technologies

We have developed a new approach for monitoring the metabolic dynamics in microbial ecosystems using a combination of DNA fingerprinting and metabolome analysis based on stable-isotope-labeling technologies. Stable-isotope probing of DNA (DNA-SIP) has been used previously for the evaluation of cross-feeding in microbial communities. For the development and validation of our monitoring approach, fecal microbiota were analyzed with stable-isotope-labeled glucose used as the sole carbon source. In order to link the metabolic information and the microbial variability, we performed metabolic–microbial correlation analysis based on nuclear magnetic resonance (NMR) profiles and denaturing gradient gel electrophoresis (DGGE) fingerprints, which successfully identified the glucose-utilizing bacteria and their related extracellular metabolites. Moreover, our approach revealed information regarding the carbon flux, in that the “first” wave of extracellular metabolites secreted by the glucose-utilizing bacteria were incorporated into the “secondary” group of substrate-utilizing bacteria, and that this “secondary” group further produced their own secondary metabolized substrates. Thus, this approach is a powerful tool for monitoring the metabolic dynamics in microbial ecosystems and allows for the tracking of the carbon flux within a microbial community.     

Identification and phylogeny of the small eukaryote population of raw and drinking waters

Culture-dependent and -independent methods were used to investigate the small eukaryote composition of raw and finished waters in the Norwegian cities of Oslo, Tromsø, Fredrikstad and Oppegård. Probes with general applicability to the 18S rRNA genes of the small eukaryote consortium were used for PCR-denaturing gradient gel electrophoresis (DGGE), and in the generation of clone libraries using the TOPO™ cloning and sequencing system. The chosen probes invariably gave a single band in agarose gel electrophoresis, indicating amplification of an area of similar size. DGGE and cloning analyses resolved the bands into components representing many unique amplicons. Diversity and composition in the collection were studied by DNA-sequencing, and visual examination of DGGE patterns. The cloning approach enabled the putative identification of a total of approximately 100 unique small eukaryotes. The major fraction of these represented ciliated and flagellated protozoal species. This was in keeping with the findings from protozoal cultivation. DNA from a number of multicellular eukaryotes was also detected. Amoebal and fungal DNA was rarely found. The latter may indicate a low incidence or a bias in the analysis technique. The population of small eukaryotes appears typical for pristine waters and no primary pathogens were detected by culture-independent techniques. However, the potentially pathogenic protozoa Acanthamoeba castellanii was grown on one occasion from Oslo’s drinking water.DGGE allowed the identification of fewer amplicons (by excision and sequencing of bands) than by the cloning-transformation approach. The DGGE analysis revealed clear similarities between the compositions of the raw and treated waters, indicating that cells or DNA in the raw water pass through the treatment trains. Protozoal culture and heterotrophic plate count analysis consistently revealed viable cells in both raw and treated waters in Oslo. This indicates that a fraction of the clone library represents eukaryotic species surviving the treatment trains. The analyses here presented represent the first published study of the general small eukaryotic fraction of the Capital’s drinking water, and those of three other Norwegian cities. We suggest that DGGE profiles may have a value in judging physical treatment efficacy (removal of cells), but that direct cloning and sequencing studies is more amenable for characterization of uncultured microbes.     

Analysis of the Bacterial Community in Zaopei During Production of Chinese Luzhou‐flavor Liquor

Denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene analysis were carried out to analyze the bacterial community in Zaopei during production of Chinese Luzhou‐flavor liquor. Primers PRBA338F and PRUN518R were used for DGGE. Polymerase chain reaction (PCR) for clone analysis was preformed with primers EU27F and 1490R. The results by DGGE showed that with increasing fermentation time the diversity of bacteria in Zaopei decreased and after one week, only one bacterium phylotype was dominant. Gene clone libraries (16S rRNA) containing 55 clonal sequences were constructed. The bacterial diversity shift observed by DGGE was also shown by the clone library analysis. Bacteria closely related to Lactobacillus acetotolerans appeared to play a key role during Chinese liquor fermentation.     

Determination of fruit origin by using 26S rDNA fingerprinting of yeast communities by PCR–DGGE: preliminary application to Physalis fruits from Egypt

The determination of geographical origin is a demand of the traceability system of import–export food products. One hypothesis for tracing the source of a product is by global analysis of the microbial communities of the food and statistical linkage of this analysis to the geographical origin of the food. For this purpose, a molecular technique employing 26S rDNA profiles generated by PCR–DGGE was used to detect the variation in yeast community structures of three species of Physalis fruit (Physalis ixocarpa Brat, Physalis pubescens L, Physalis pruinosa L) from four Egyptian regions (Qalyoubia, Minufiya, Beheira and Alexandria Governments). When the 26S rDNA profiles were analysed by multivariate analysis, distinct microbial communities were detected. The band profiles of Physalis yeasts from different Governments were specific for each location and could be used as a bar code to discriminate the origin of the fruits. This method is a new traceability tool which provides fruit products with a unique biological bar code and makes it possible to trace back the fruits to their original location. Copyright © 2009 John Wiley & Sons, Ltd.