1,721,027 research outputs found
Dynamic of functional microbial groups during mesophilic composting of agro-industrial wastes and free-living (N2)-fixing bacteria application
No full textAlthough several reports are available concerning the composition and dynamics of the microflora during the composting of municipal solid wastes, little is known about the microbial diversity during the composting of agro-industrial refuse. For this reason, the first parts of this study included the quantification of microbial generic groups and of the main functional groups of C and N cycle during composting of agro-industrial refuse. After a generalized decrease observed during the initial phases, a new bacterial growth was observed in the final phase of the process. Ammonifiers and (N2)-fixing aerobic groups predominated outside of the piles whereas, nitrate-reducing group increased inside the piles during the first 23days of composting. Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), showed an opposite trend of growth since ammonia oxidation decreased with the increase of the nitrite oxidation activity. Pectinolytics, amylolytics and aerobic cellulolytic were present in greater quantities and showed an upward trend in both the internal and external part of the heaps. Several free-living (N2)-fixing bacteria were molecularly identify as belonging especially to uncommon genera of nitrogen-fixing bacteria as Stenotrophomonas, Xanthomonas, Pseudomonas, Klebsiella, Alcaligenes, Achromobacter and Caulobacter. They were investigated for their ability to fix atmospheric nitrogen to employ as improvers of quality of compost. Some strains of Azotobacter chrococcum and Azotobacter salinestris were also tested. When different diazotrophic bacterial species were added in compost, the increase of total N ranged from 16% to 27% depending on the selected microbial strain being used. Such microorganisms may be used alone or in mixtures to provide an allocation of plant growth promoting rhizobacteria in soil. Copyright 2013 Elsevier Ltd. All rights reserved
Cellulolytic Bacillus strains from natural habitats - A review
No full textFossil fuel reserves depletion, global warming, costly and problematic waste recycling and population growth greatly induce to fi nd renewable energy sources. Second generation bioethanol produced from lignocellulosic materials exhibits great potential as liquid biofuel to substitute gasoline. Production costs of enzymes involved in cellulose hydrolysis into fermentable sugars represent the main obstacle to achieve competitive production of cellulosic ethanol. Cheaper and more effi cient biocatalysts for the saccharifi cation step are, therefore, required for making the whole process more competitive. The biodiversity of natural niches has been so far exploited for the isolation of new cellulolytic microorganisms whose enzymes are naturally evolved for an effi cient conversion of cellulose into fermentable sugars. This review discusses advances in isolation of bacteria, namely Bacillus spp., from several natural habitats and their ability to produce cellulase activity
Microbiological and physic-chemical characterization during chestnut composting for sustainable fertilization.
No full textMicrobial characterization of sourdough for sweet baked products in the Campania region (southern Italy) by a polyphasic approach
No full textThe microflora of nine sourdoughs used for sweet bakery products underwent preliminary microbiological characterization using lactic acid bacteria (LAB) and yeast enumeration. Five sourdough samples were submitted for microbial identification by culture-dependent techniques employing 16S and 26S rRNA genes sequencing, as well as a culture-independent technique using PCR-DGGE analysis. The LAB species isolated belonged principally to facultative heterofermentative Lactobacillus spp., Leuconostoc spp., and Lactococcus spp. Yeast strains were identified as Saccharomyces cerevisiae, with one exception represented by a strain belonging to Metschnikowia pulcherrima. PCR-DGGE analysis allowed the identification of Streptococcus thermophilus, Lactobacillus sakei, Weissella groceries and Lactobacillus sanfranciscensis among lactic acid bacteria and Saccharomyces cerevisiae and Metschnikowia pulcherrima among yeasts. This polyphasic approach highlighted different levels of biodiversity, from two to eight different typical LAB species, always associated to Saccharomyces cerevisiae, that could be selected to be specifically used in naturally fermented brioche and cornetto preparation
Effect of sourdough at different concentrations on quality and shelf life of bread
No full textThe objective of this work was to study the effect of sourdough obtained with selected exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) strains on the quality of bread and its shelf life. Two sourdough concentrations were used in order to ascertain the best bread composition. Fresh bread quality was studied by means of microbiological, physical, chemical and mechanical analysis, whereas physical, thermal and mechanical properties were investigated to study the product shelf life. The results showed that dough prepared with 30g/100g of sourdough had a negative impact on bread quality properties in the absence of EPS-producing LAB strains, whereas the opposite was observed in the presence of EPS-producing strains: bread samples at 30g/100g of sourdough showed higher volume, higher moisture content and better mechanical properties during storage than samples at 20g/100g of sourdough. Moreover, 30g/100g of sourdough showed a protective effect on bread staling, thus confirming the effect of sourdough concentration and the positive role of EPS on functional propertie
Genetic diversity of a natural population of Rhizobium leguminosarum bv. viciae nodulating plants of Vicia faba in the Vesuvian area
No full textA total of 98 rhizobial strains, isolated during the winter of the years 2003 (35 isolates), 2004 (33 isolates), and 2005 (30 isolates) were analyzed to determine the genetic diversity of the natural population nodulating Vicia faba plants and to identify dominant genotypes. All isolates were identified as Rhizobium leguminosarum bv. viciae by biovar-specific polymerase chain reaction amplification of the nodC gene. Intraspecific DNA polymorphism was evaluated through the restriction endonucleases analysis combined with pulsed-field gel electrophoresis. Four genotypes characterized 53% of the isolates, showing a high occurrence; moreover, they were recovered over the 3 years, thus showing a lasting persistence in the soil, which could mean a high degree of saprophytic competitiveness. The richness, diversity, and dominance indexes of genotypes were calculated to monitor the evolution of the rhizobial population during the 3 years. The genetic diversity of the analyzed strains decreased along the 3 years. In fact, the biodiversity index H' decreased from 2.6 in the first and second year to 1.9 in the third year; probably, as a result of bean monocropping, specific genotypes of Rh. leguminosarum bv. viciae were naturally selected
Removal of polycyclic aromatic hydrocarbons (PAHs) by selected microbial strains isolated from highly contaminated soil
No full textPrebiotic content of bread prepared with flour from immature wheat grain and selected dextran-producing lactic Acid bacteria.
No full textIn the last few years the need to produce food with added value has fueled the search for new ingredients and health-promoting compounds. In particular, to improve the quality of bakery products with distinct nutritional properties, the identification of new raw materials, appropriate technologies, and specific microbial strains is necessary. In this study, different doughs were prepared, with 10% and 20% flour from immature wheat grain blended with type "0 America" wheat flour. Immature flour was obtained from durum wheat grains harvested 1 to 2 weeks after anthesis. Doughs were obtained by both the straight-dough and sourdough processes. Two selected exopolysaccharide-producing strains of lactic acid bacteria (LAB), Leuconostoc lactis A95 and Lactobacillus curvatus 69B2, were used as starters. Immature flour contained 2.21 g/100 g (dry weight) of fructo-oligosaccharides. Twenty percent immature flour in dough resulted in a shorter leavening time (4.23 0.03 h) than with the control and dough with 10% immature flour. The total titratable acidity of sourdough with 20% immature flour was higher (12.75 0.15 ml 0.1 N NaOH) than in the control and sourdough with 10% immature wheat flour (9.20 ml 0.1 N NaOH). Molecular analysis showed that all samples contained three LAB species identified as L. lactis, L. curvatus, and Pediococcus acidilactici. A larger amount of exopolysaccharide was found in sourdough obtained with 20% immature flour (5.33 0.032 g/kg), positively influencing the exopolysaccharide content of the bread prepared by the sourdough process (1.70 0.03 g/kg). The addition of 20% immature flour also led to a greater presence of fructo-oligosaccharides in the bread (900 mg/100 g dry weight), which improved its nutritional characteristics. While bread volume decreased as the concentration of immature wheat flour increased, its mechanical characteristics (stress at a strain of 30%) were the same in all samples obtained with different percentages of fructo-oligosaccharides. These data support the use of immature wheat grain flour, and exopolysaccaride-producing lactic acid bacteria in formulating functional prebiotic baked goods whose nutritional value can be suitably improved
Development of in vitro screening method to select EPS-producing LAB for cereal based products
No full textIsolation, selection and improvement of a Methylbacterium spp. strain for the bioremediation of anthropogenic organic compounds
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