Primary metabolism in <Emphasis Type="Italic">Lactobacillus sakei</Emphasis> food isolates by proteomic analysis

Background  

Lactobacillus sakei is an important food-associated lactic acid bacterium commonly used as starter culture for industrial meat fermentation, and with great potential as a biopreservative in meat and fish products. Understanding the metabolic mechanisms underlying the growth performance of a strain to be used for food fermentations is important for obtaining high-quality and safe products. Proteomic analysis was used to study the primary metabolism in ten food isolates after growth on glucose and ribose, the main sugars available for L. sakei in meat and fish.     

Note on the food habits of Ptilocercus lowii Gray (Pentail tree-shrew) and Echinosorex gymnurus (Raffles) (Moonrat) in Malaya with remarks on "ecological labelling" by parasite patterns

Examination of the endoparasites and stomach contents of Moonrats and Pentail treeshrews helps to establish certain facts as to the behaviour and food preference in their natural environment. Earthworms and arthropods are the main diet of Moonrats in the wild, with fish, crabs and land molluscs as supplementary food. In captivity, this animal fed primarily on fresh fish. The Pentail tree-shrews, on the other hand are more insectivorous although meat is occasionally eaten. This animal apparently is not strictly a canopydweller as was previously believed. The stomach contents, and the fact that some specimens were trapped on the forest floor indicates that they may often descend to ground level.     

Autophagy: from basic research to its application in food biotechnology

Autophagy is a catabolic process by which the cytoplasm is sequestered into double-membrane vesicles and delivered to the lysosome/vacuole for breaking down and recycling of the low molecular weight degradation products. The isolation in the yeast Saccharomyces cerevisiae of many of the genes involved in autophagy constituted a milestone in understanding the molecular bases of this pathway. The identification of ortholog genes in other eukaryotic models revealed that the mechanism of autophagy is conserved among all eukaryotes. This pathway has been shown to be involved in a growing number of physiological processes and conversely, its deregulation may contribute to the development of several diseases. Recent reports have also shown that autophagy may play an important role in biotechnological processes related with the food industry. In this review we discuss current knowledge of the molecular mechanism of autophagy, including some applied aspects of autophagy in the field of food biotechnology.     

Biology of the red yeastXanthophyllomyces dendrorhous (Phaffia rhodozyma)

Phaffia rhodozyma is a red-pigmented basidiomycetous yeast that produces astaxanthin. Because of this property, it is fermented commercially on a large scale. Astaxanthin is used as a food colorant for fish, and as an antioxidant, it is potentially useful in the human pharmaceutical industry. This review summarizes the published biology of this yeast: its morphology and ultrastructure, organization of the cytoskeleton, and the nuclear and extrachromosomal genomes. Alteration of sexual and vegetative phases in the life cycle and its biotechnological importance are also described.     

Microbial transglutaminase and its application in the food industry. A review

The extremely high costs of manufacturing transglutaminase from animal origin (EC 2.3.2.13) have prompted scientists to search for new sources of this enzyme. Interdisciplinary efforts have been aimed at producing enzymes synthesised by microorganisms which may have a wider scope of use. Transglutaminase is an enzyme that catalyses the formation of isopeptide bonds between proteins. Its cross-linking property is widely used in various processes: to manufacture cheese and other dairy products, in meat processing, to produce edible films and to manufacture bakery products. Transglutaminase has considerable potential to improve the firmness, viscosity, elasticity and water-binding capacity of food products. In 1989, microbial transglutaminase was isolated from Streptoverticillium sp. Its characterisation indicated that this isoform could be extremely useful as a biotechnological tool in the food industry. Currently, enzymatic preparations are used in almost all industrial branches because of their wide variety and low costs associated with their biotechnical production processes. This paper presents an overview of the literature addressing the characteristics and applications of transglutaminase.     

Lactic-acid fermentation as a low-cost means of food preservation in tropical countries

Abstract The range of traditional lactic-acid-fermented foods in tropical countries is briefly reviewed. Recent studies on the lactic acid fermentation of fish and cassava products are described. Lactic-acid-fermented fish products may offer considerable scope for the development of new food products and for the use of under-utilised fish species. Lactic-acid-fermented fish products are common in parts of Asia; methods to improve the product and shelf-life quality, to reduce microbial risks and to accelerate the process are described. This work is based on fish/salt/carbohydrate model systems. The nutritional aspects of cassava fermentation are discussed with respect to factors involved in determining residual cyanide levels; the possible anti-nutritional rôle of condensed tannins is mentioned. The increasing consumption of meat products in tropical countries emphasises the need for a preservation method that does not depend on refrigeration. The possible production of sausage ingredients preserved by lactic acid fermentation, and the associated research needs are described.     

Fish Growth in Marine Culture Systems: A Challenge for Biotechnology

Aquaculture production is constrained largely by the growth efficiency of the species being produced. Nutritional approaches have played an important part in improving this situation, but, it is argued, the room for further improvement using such established techniques is limited. Alternative ways of improving fish production by utilizing recent biotechnological advances are explored and assessed as to their potential for commercialization in the near future. Transgenic technologies promise a revolution in aquaculture, but it is considered that consumer resistance may delay the use of transgenic fish for food production. An alternative approach could be the breeding of transgenic fodder plants without the amino acid deficiencies of existing alternatives to fish meal in aquaculture diets. The use of probiotics could reduce antibiotic use on fish farms while they might also provide the basis for ``smart' diets, tailored to specific purposes by the inclusion of microorganisms. The selection and genetic engineering of nitrifying and denitrifying bacteria could also pave the way for fully enclosed, recirculating marine culture systems, which would allow control of the environmental variables that currently restrain marine fish culture. Received August 10, 1998; accepted October 8, 1998.     

Harvesting for food versus feed: a review of Peruvian fisheries in a global context

Peru is the top exporter of fishmeal and fish oil (FMFO) worldwide and is responsible for half and a third of global production, respectively. Landings of “anchoveta” (Engraulis ringens) are used nearly exclusively for FMFO production, despite a proactive national food policy aimed at favoring the direct human consumption of this inexpensive species. It may be surprising that in a country where malnutrition and caloric deficit constitute major issues, a low-priced and highly nutritious fish such as anchovy does not have stronger domestic demand as a food fish. Here, we review and assess eight potential politico-socio-economic processes that can explain this situation. The main explanation are dietary habits, the preference for broiler and the higher profit from anchovy sold as feed fish compared to its use as a food fish due to historically high FMFO prices, boosted by an increasing demand for aquaculture in a context of finite forage and trash fish resources. In addition, the recent introduction of an individual quota system has shifted bargaining power from processors to fishers, thereby increasing competition for the raw material. This competition results in an increase in anchovy prices offered by the feed fish industry due to its onshore processing overcapacity, which is detrimental to the food fish industry. In the end, although the dominant use of anchovy for fish feed is largely explained by integrating these market mechanisms and other minor ones, this use raises other issues, such as rent redistribution through public policies, employment, equitability and utility (low social costs), and resource management (threats to ecosystems or global change). Different policy scenarios are proposed in relation to these issues.     

Importance of fish behaviour in modelling conservation problems: food limitation as an example

Simulation experiments using the inSTREAM individual-based brown trout Salmo trutta population model explored the role of individual adaptive behaviour in food limitation, as an example of how behaviour can affect managers' understanding of conservation problems. The model includes many natural complexities in habitat (spatial and temporal variation in characteristics such as depth and velocity, temperature, hiding and feeding cover, drift-food supply and predation risk), fish physiology (especially, how food intake and growth vary with hydrodynamics, cover, fish size and temperature) and behaviour. When drift-food concentration was increased over a wide range in 7 year simulations, the simulated population was always food limited. In fact, as food supply increased, the population increased at an increasing rate and consumed a higher percentage of the food supply, apparently because higher food concentrations make more stream area energetically profitable for drift feeders. The behaviour most responsible for this response was activity selection: when food was abundant, fish chose to feed less frequently and more nocturnally, thereby reducing predation mortality so more fish survived longer. These results indicate that the traditional concept of food limitation, that food availability stops limiting population size when it exceeds some threshold level, may not be useful and can be misleading. Results also strongly contradict the concept that a salmonid population is not food limited if the total food supply is greater than the population's consumption. Explicit consideration of adaptive behaviour produced a novel but believable understanding of food effects on salmonid populations. Published 2011. This article is a U.S. Government work and is in the public domain in the USA.     

Incidence and identification of mesophilic Aeromonas spp. from retail foods

Sixty-eight food samples were examined for the presence of mesophilic Aeromonas species both qualitatively and quantitatively. Aeromonads were isolated from 26% of the vegetable samples, 70% of the meat and poultry samples and 72% of the fish and shrimps. Numbers of motile aeromonads present in the food samples varied from <10(2) cfu g(-1) to >10(5) cfu g(-1). GLC analysis of FAMEs was used to identify a selection of presumptive Aeromonas colonies to fenospecies or genomic species level. Aeromonas strains belonging to the Aer. caviae complex, which also includes the potentially pathogenic genospecies HG4, were mostly isolated from vegetables but were also found in meat, poultry and fish. In addition, three strains of the virulent taxon Aer. veronii biovar sobria HG8 were isolated from poultry and minced meat. All members of the Aer. hydrophila complex, predominant in the fish, meat and poultry samples, were classified in the non-virulent taxon HG3. Although the significance of Aeromonas in foods remains undefined, the isolation of Aeromonas HG4 and HG8 strains from a variety of retail foods may indicate that these products can act as possible vehicles for the dissemination of food-borne Aeromonas gastroenteritis.     

Gamete interactions in teleost fish: the egg envelope. Basic studies and perspectives as environmental biomonitor

The current knowledge about teleost fish egg envelope is summarized. The paper analyzes the organization and deposition process of the protein composition and genes involved in the synthesis of teleost fish egg envelopes and their role in gamete interaction during fertilization. Pelagic and demersal species that our research group is working with are especially considered. The vertebrate ZP family of proteins, the evolution and relationship among the different genes and their expression are taken into account. We consider fish envelope as a possible biomonitor for ecological contaminants. The biotechnological applications for aquaculture and genomic and post-genomic approaches are auspicious.     

Intraspecies Genomic Diversity and Natural Population Structure of the Meat-Borne Lactic Acid Bacterium Lactobacillus sakei

Lactobacillus sakei is a food-borne bacterium naturally found in meat and fish products. A study was performed to examine the intraspecies diversity among 73 isolates sourced from laboratory collections in several different countries. Pulsed-field gel electrophoresis analysis demonstrated a 25% variation in genome size between isolates, ranging from 1,815 kb to 2,310 kb. The relatedness between isolates was then determined using a PCR-based method that detects the possession of 60 chromosomal genes belonging to the flexible gene pool. Ten different strain clusters were identified that had noticeable differences in their average genome size reflecting the natural population structure. The results show that many different genotypes may be isolated from similar types of meat products, suggesting a complex ecological habitat in which intraspecies diversity may be required for successful adaptation. Finally, proteomic analysis revealed a slight difference between the migration patterns of highly abundant GapA isoforms of the two prevailing L. sakei subspecies (sakei and carnosus). This analysis was used to affiliate the genotypic clusters with the corresponding subspecies. These findings reveal for the first time the extent of intraspecies genomic diversity in L. sakei. Consequently, identification of molecular subtypes may in the future prove valuable for a better understanding of microbial ecosystems in food products.     

长吻和南方大口鲶胃肠道消化能力的研究

通过对长吻（Ｌｅｉｏｃａｓｉｓｌｏｎｇｉｒｏｓｔｒｉｓ）、南方大口鲶（Ｓｉｌｕｒｕｓｍｅｒｉｄｉｏｎａｌｉｓ）胃、肠道所作大体解剖观察对比、粘膜扫描电镜观察、蛋白酶和淀粉酶活力测定等的研究结果表明,南方大口鲶的胃壁和胃粘膜皱褶非常发达,其伸缩能力远强于长吻。但长吻的胃、肠粘膜的分泌功能较南方大口鲶强,其蛋白酶和淀粉酶活力强于相近体重的南方大口鲶。南方大口鲶的发达的胃壁作用可能在于有较强的伸张能力以便一次性地食贮较多或较大个体食物,并在胃内进行初步消化。总体评价,长吻一次性的摄食能力不如南方大口鲶,但对同种食物的消化能力强于相近或相同体重的南方大口鲶。南方大口鲶胃、肠道消化生理特点适于一次捕食较大个体食物,具间歇性摄食的消化生理特点。而长吻则适于以较高摄食频率和对食物较强的消化利用率以适应营养的需要。     

comK prophage junction fragments as markers for Listeria monocytogenes genotypes unique to individual meat and poultry processing plants and a model for rapid niche-specific adaptation, biofilm formation, and persistence

Different strains of Listeria monocytogenes are well known to persist in individual food processing plants and to contaminate foods for many years; however, the specific genotypic and phenotypic mechanisms responsible for persistence of these unique strains remain largely unknown. Based on sequences in comK prophage junction fragments, different strains of epidemic clones (ECs), which included ECII, ECIII, and ECV, were identified and shown to be specific to individual meat and poultry processing plants. The comK prophage-containing strains showed significantly higher cell densities after incubation at 30°C for 48 h on meat and poultry food-conditioning films than did strains lacking the comK prophage (P < 0.05). Overall, the type of strain, the type of conditioning film, and the interaction between the two were all highly significant (P < 0.001). Recombination analysis indicated that the comK prophage junction fragments in these strains had evolved due to extensive recombination. Based on the results of the present study, we propose a novel model in which the concept of defective comK prophage was replaced with the rapid adaptation island (RAI). Genes within the RAI were recharacterized as "adaptons," as these genes may allow L. monocytogenes to rapidly adapt to different food processing facilities and foods. If confirmed, the model presented would help explain Listeria's rapid niche adaptation, biofilm formation, persistence, and subsequent transmission to foods. Also, comK prophage junction fragment sequences may permit accurate tracking of persistent strains back to and within individual food processing operations and thus allow the design of more effective intervention strategies to reduce contamination and enhance food safety.     

Growth and social interactions of wild and sea-ranched brown trout and their hybrids

A laboratory study of the social behaviour and growth performance of juvenile brown trout Salmo trutta of wild and sea-ranched origin and their crosses, indicated that the social behaviour of wild and sea-ranched fish differed. Male and female parents seemed to have a different impact on the juveniles. The category having wild mother and sea-ranched father were less aggressive, less active in general, but active in feeding, and therefore had higher growth rates. This pattern arose despite that the feeding rate and the motivation to first get a food item when food was provided did not differ between the groups of fish. Wild fish tended to be most aggressive. If sea-ranched and wild fish have different intrinsic (genetically based) 'life styles', the crosses between wild and sea-ranched fish indicate that there is likelihood for an introgression of genes adapted to hatchery environment into the genetics of wild conspecifics. This is particularly serious when hatchery-reared fish invades wild populations over many years.     

APPLICATION OF POLYMERASE CHAIN REACTION-OLIGONUCLEOTIDE LIGATION ASSAY FOR THE DETECTION OF SALMONELLAE IN PROCESSED MEAT, POULTRY, FISH, AND PET FOODS

We have tested a rapid and sensitive DNA-based assay for the detection of Salmonella serovars in a number of different processed meat, fish, poultry, and pet food samples. This technique uses an enrichment broth cultivation followed by a Salmonella-specific polymerase chain reaction (PCR) and oligonucleotide ligation assay (OLA) to specifically detect amplified PCR products in an ELISA-based microtiter plate format. The combined cultivation and PCR-OLA techniques were compared with a conventional culture method and with DNA hybridizations of PCR products for the detection of Salmonella bacteria. Eighty-one different processed meat, poultry, and pet food samples were screened for the presence of Salmonella serovars after 24 h and 48 h of enrichment broth cultivation. After 24 h of incubation, one ground turkey sample was positive by both culture and PCR-OLA (100% sensitivity and 100% specificity). After 48 h of incubation, two additional samples (ground beef and a dog food sample) were positive by both culture and PCR-OLA (100% sensitivity and 100% specificity), and three other samples (two ground beef samples and one ground turkey) were positive only by PCR-OLA (96.1% specificity). All positive PCR-OLA results were confirmed in DNA hybridizations with an oligonucleotide specific for the amplified PCR product. When compared to conventional culture, the combined 48 h enrichment and PCR-OLA had a positive predictive value of 50% and a negative predictive value of 100%. We concluded that a combined cultivation and PCR-OLA could be used as a sensitive and specific presumptive screening method for detecting Salmonella serovars in processed meat, fish, poultry, and pet foods.     

水螅的替代食物筛选

在水螅的培养中,常出现食物缺乏。为了获得替代食物,比较水螅对一些常见肉类的捕食行为。结果表明,水螅对蚯蚓肉、虾肉、鱼肉、鸡肉、牛肉和猪肉均能捕捉,对各食物的捕捉比例无显著差异;但水螅对食物的摄食比例在食物类型间存在显著差异,对虾肉较为偏好。可选择虾肉作为培养时的替代食物。