B. Juárez-Jiménez

Antimicrobial activity of olive mill wastewaters (alpechin) and biotransformed olive oil mill wastewater

Abstract Olive oil extraction produces a great volume of residue. These olive mill wastes are known as alpechin. This wastewater is a powerful pollutant, resistant to degradation and presents a severe environmental problem related to its high organic content made up largely of simple phenolic compounds, that have been described as being both antimicrobial and phytotoxic. This paper reviews briefly the antimicrobial activity of olive mill wastewaters and provides evidence to show the potential of micro organisms ( Bacillus pumilus ) to reduce the phenol content of alpechin, and also that biotransformation depends on the dilution (v/v) of the alpechin. Furthermore, we sought to provide a real evaluation of the extent of alpechin biotransformation. This was achieved by means of an internal reference, i.e. in relative terms, the phenol content resulting from the biotransformation process. The phenol content was measured using HPLC techniques, and results were obtained showing that the bacterium had most effect in reducing the phenol content of alpechin at concentrations of between 40 and 100%. It was also observed that at concentrations of 80%, in addition to a slight reduction in total phenols, new phenolic compounds, not present in the original alpechin, were generated.

Bacterial community structure and enzyme activities in a membrane bioreactor (MBR) using pure oxygen as an aeration source

A pilot-scale membrane bioreactor was used to treat urban wastewater using pure oxygen instead of air as a source of aeration, to study its influence on bacterial diversity and levels of enzyme activities (acid and alkaline phosphatases, glucosidase, protease, and esterase) in the sludge. The experimental work was developed in two stages influenced by seasonal temperature. Operational parameters (temperature, pH, BOD5, COD, total and volatile suspended solids) were daily monitored, and enzyme activities measured twice a week. Redundancy analysis (RDA) was used to reveal relationships between the level of enzyme activities and the variation of operational parameters, demonstrating a significant effect of temperature and volatile suspended solids. Bacterial diversity was analyzed by temperature-gradient gel electrophoresis of PCR-amplified partial 16S rRNA genes. Significant differences in community structure were observed between both stages. Sequence analysis revealed that the prevalent Bacteria populations were evolutively close to Alphaproteobacteria (44%), Betaproteobacteria (25%) and Firmicutes (17%).

Physiologic and metabolic characterization of a new marine isolate (BM39) of Pantoea sp. producing high levels of exopolysaccharide

BackgroundMarine environments are the widest fonts of biodiversity representing a resource of both unexploited or unknown microorganisms and new substances having potential applications. Among microbial products, exopolysaccharides (EPS) have many physiological functions and practical applications. Since EPS production by many bacteria is too scarce for practical use and only few species are known for their high levels of production, the search of new high EPS producers is of paramount importance. Many marine bacteria, that produce EPS to cope with strong environmental stress, could be potentially exploited at the industrial level.ResultsA novel bacterium, strain BM39, previously isolated from sediments collected in the Tyrrhenian Sea, was selected for its production of very high levels of EPS. BM39 was affiliated to Pantoea sp. (Enterobacteriaceae) by 16S rRNA gene sequencing and biochemical tests. According to the phylogenetic tree, this strain, being quite far from the closest known Pantoea species (96% identity with P. agglomerans and P. ananatis) could belong to a new species. EPS production was fast (maximum of ca. 21 g/L in 24 h on glucose medium) and mainly obtained during the exponential growth. Preliminary characterization, carried out by thin layer and gel filtration chromatography, showed that the EPS, being a glucose homopolymer with MW of ca. 830 kDa, appeared to be different from those of other bacteria of same genus. The bacterium showed a typical slightly halophilic behavior growing optimally at NaCl 40 ‰ (growing range 0-100 ‰). Flow cytometry studies indicated that good cell survival was maintained for 24 h at 120 ‰. Survival decreased dramatically with the increase of salinity being only 1 h at 280 ‰. The biochemical characterization, carried out with the Biolog system, showed that MB39 had a rather limited metabolic capacity. Its ability, rather lower than that of P. agglomerans, was almost only confined to the metabolization of simple sugars and their derivatives. Few alcohols, organic acids and nitrogen compounds were partially used too.ConclusionsStrain BM39, probably belonging to a new species, due to its remarkable EPS production, comparable to those of known industrial bacterial producers, could be suggested as a new microorganism for industrial applications.

Screening for extracellular enzyme activities by bacteria isolated from samples collected in the Tyrrhenian Sea

Ninety-five bacterial isolates, obtained in pure cultures from samples collected in various sites of the East sector of the Tyrrhenian Sea, were plate-screened for their ability to produce twelve extracellular enzyme activities in order to find new strains for possible applications. Lipases, DNAase and RNAase were generally present; amilase, phosphatase, pectinase and protease were common. Chitinase and urease were present in a limited number of isolates while glucose oxidase and phenol oxidase were quite rare. Few isolates, producing a limited number of enzymes, could have a low eco-nutritional versatility while most of them, showing a diversified enzymatic competence, are probably more advantaged in the marine environment. However, none of the isolates was able to produce all the tested activities. Few strains (14) showed apparent high level of some extracellular enzyme activities and could be considered as potential high-producers.

Interlinkages between bacterial populations dynamics and the operational parameters in a moving bed membrane bioreactor treating urban sewage.

Bacteria are key players in biological wastewater treatments (WWTs), thus a firm knowledge of the bacterial population dynamics is crucial to understand environmental/operational factors affecting the efficiency and stability of the biological depuration process. Unfortunately, little is known about the microbial ecology of the advanced biological WWTs combining suspended biomass (SB) and attached biofilms (AB). This study explored in depth the bacterial community structure and population dynamics in each biomass fraction from a pilot-scale moving bed membrane bioreactor (MBMBR) treating municipal sewage, by means of temperature-gradient gel electrophoresis (TGGE) and 454-pyrosequencing. Eight experimental phases were conducted, combining different carrier filling ratios, hydraulic retention times and concentrations of mixed liquor total suspended solids. The bacterial community, dominated by Proteobacteria (20.9-53.8%) and Actinobacteria (20.6-57.6%), was very similar in both biomass fractions and able to maintain its functional stability under all the operating conditions, ensuring a successful and steady depuration process. Multivariate statistical analysis demonstrated that solids concentration, carrier filling ratio, temperature and organic matter concentration in the influent were the significant factors explaining population dynamics. Bacterial diversity increased as carrier filling ratio increased (from 20% to 35%, v/v), and solids concentration was the main factor triggering the shifts of the community structure. These findings provide new insights on the influence of operational parameters on the biology of the innovative MBMBRs.

Bacterial community structure of a coastal area in Kandalaksha Bay, White Sea, Russia: possible relation to tidal hydrodynamics

Kandalaksha Bay is an estuarine system located around the North Polar Circle in the White Sea (Russia). This peculiar environment, showing big sea level differences during tide cycles causing intense water mixing, is almost unknown concerning its microbial diversity. In this work, seawater bacterial communities, mainly obtained from a coastal area, were studied in order to gather information on their structure and most abundant populations. The study was carried out by cluster analysis of polymerase chain reaction–temperature-gradient gel electrophoresis (PCR-TGGE) fingerprinting of partial 16S-rRNA gene amplicons. Bacterial communities were strongly homogenized by tidal water mixing, especially on surface layers and close to the shore. Samples collected from the intertidal zone and the nearby sea surface grouped together with a high percentage of similarity, while those taken offshore at various depths showed evident differences. Multivariate analysis indicated depth as the most significant environmental parameter causing variations in the community structure. High levels of diversity were revealed by both the Simpson’s index of diversity and the range-weighted richness index. The functional organization index suggested that the community was potentially able to preserve its functionality under stressing environmental perturbations. Sequencing of TGGE bands showed that most of the bacteria populations were evolutionarily close to α-proteobacteria. Some γ-proteobacteria and Actinobacteria were revealed too. This work represents the first major contribution to understanding bacterial diversity in Kandalaksha Bay.