Mercedes Monteoliva-Sánchez

Bioremediation and biovalorisation of olive-mill wastes

Olive-mill wastes are produced by the industry of olive oil production, which is a very important economic activity, particularly for Spain, Italy and Greece, leading to a large environmental problem of current concern in the Mediterranean basin. There is as yet no accepted treatment method for all the wastes generated during olive oil production, mainly due to technical and economical limitations but also the scattered nature of olive mills across the Mediterranean basin. The production of virgin olive oil is expanding worldwide, which will lead to even larger amounts of olive-mill waste, unless new treatment and valorisation technologies are devised. These are encouraged by the trend of current environmental policies, which favour protocols that include valorisation of the waste. This makes biological treatments of particular interest. Thus, research into different biodegradation options for olive-mill wastes and the development of new bioremediation technologies and/or strategies, as well as the valorisation of microbial biotechnology, are all currently needed. This review, whilst presenting a general overview, focusses critically on the most significant recent advances in the various types of biological treatments, the bioremediation technology most commonly applied and the valorisation options, which together will form the pillar for future developments within this field.

Production of a Metal-Binding Exopolysaccharide by Paenibacillus jamilae Using Two-Phase Olive-Mill Waste as Fermentation Substrate

The present study investigated the use of two-phase olive mill waste (TPOMW) as substrate for the production of exopolysaccharide (EPS) by the endospore-forming bacilli Paenibacillus jamilae. This microorganism was able to grow and produce EPS in aqueous extracts of TPOMW as a unique source of carbon. The effects of substrate concentration and the addition of inorganic nutrients were investigated. Maximal polymer yield in 100-ml batch-culture experiments (2 g l−1) was obtained in cultures prepared with an aqueous extract of 20% TPOMW (w/v). An inhibitory effect was observed on growth and EPS production when TPOMW concentration was increased. Nutrient supplementation (nitrate, phosphate, and other inorganic nutrients) did not increase yield. Finally, an adsorption experiment of Pb (II), Cd (II), Cu (II), Zn (II), Co (II), and Ni (II) by EPS is reported. Lead was preferentially complexed by the polymer, with a maximal uptake of 230 mg/g EPS.

Halorubrum tebenquichense sp. nov., a novel halophilic archaeon isolated from the Atacama Saltern, Chile

A novel extremely halophilic archaeon was isolated from Lake Tebenquiche, situated in the northern part of the Atacama Saltern, Chile. The cells of these micro-organisms were mostly irregularly disc-shaped. They grew in medium containing saturated concentrations of NaCl and did not require magnesium for optimal growth. The polar lipid composition revealed the presence of mannosyl-2-sulfate-(1-4)-glycosyl-archaeol, the main glycolipid of the genus Halorubrum, and two new glycolipids. The G+C content of the DNA was 63.2 mol%. Phylogenetic analysis of the 16S rRNA gene placed strain ALT6-92T within the Halorubrum cluster. The low DNA-DNA hybridization value justified classification in a new species for which the name Halorubrum tebenquichense sp. nov. is proposed. The type strain is ALT6-92T (= CECT 5317T = DSM 14210T).

Administration of Lactobacillus casei and Lactobacillus plantarum affects the diversity of murine intestinal lactobacilli, but not the overall bacterial community structure.

Lactobacilli are normal inhabitants of the gastrointestinal tract (GIT) of many mammalian hosts. Their administration as probiotics in functional foods is currently a frequent practice, mainly because of their benefits to host health. It is therefore of interest to study the impact of administration of exogenous strains of Lactobacillus normally used as probiotics upon endogenous microbial populations. For this purpose, fecal and intestinal tissue samples were analyzed in a mouse model fed with a mixture of Lactobacillus plantarum and Lactobacillus casei isolated from commercially available dairy products. The murine intestinal microbiota was studied by means of cultivation-independent 16S rRNA gene-targeted techniques, namely denaturing gradient gel electrophoresis (DGGE), terminal restriction fragment length polymorphism (T-RFLP) and sequence analysis of clone libraries. Multivariate statistical analysis was used to integrate datasets obtained from the different techniques applied. Whereas no differences were detected in the composition of the overall fecal bacterial community, changes were observed for intestinal tissue samples. Moreover, an increase in the diversity of gut lactobacilli was observed in fecal as well as intestinal tissue samples when mice received the mixture of L. casei and L. plantarum.

The effect of salinity and compatible solutes on the biosynthesis of cyclopropane fatty acids in Pseudomonas halosaccharolytica

SUMMARY: The moderately halophilic eubacterium Pseudomonas halosacchavolytica has been grown at salinities over the range 5-25 % (w/v), equivalent to 0.7-3.5 M-NaCl, and the fatty acid composition determined in the late-exponential and stationary phases of batch culture. There was an increase in the proportion of cyclopropane fatty acids (CFA) as the cultures went into stationary phase at all salinities; the overall proportion of CFA was higher in the media containing more salt. The biosynthesis of CFA in P. halosacchavolytica was determined using radiolabelled S-adenosylmethionine as the precursor incubated in cell-free extracts prepared by breaking bacteria with a French press. Compared with the activity obtained in 100 mM-phosphate buffer, the activity of CFA synthetase was inhibited by the addition of NaC1 or KC1, but stimulated up to 12-fold by added glycinebetaine, with maximum activity at 3 M. Although the specific activity of CFA synthetase in lysates from cultures grown in 0.7 or 2.1 M-NaC1 were similar in the presence of 3 M-glycinebetaine, the enzyme activity in low-salinity cultures was better adapted to function in 1 M-glycinebetaine. Shift-up experiments, in which CFA synthetase activity was assayed in cell-free extracts prepared at different times after increasing culture salinity from 0.7 to 2.1 M-NaC1, showed that the activity of the enzyme was immediately responsive to compatible solute concentration changes and indicated that enzyme induction would not be required to achieve the salt-dependent alterations in membrane lipid CFA composition in vivo. A range of other compatible organic solutes stimulated CFA synthetase activity to a much lesser extent (1.8-fold) compared with glycinebetaine. It is suggested that a compatible solute, which is normally accumulated during osmo(halo)adaptation by an organism in order to contribute towards osmotic balance, does not behave passively towards intracellular proteins but can also stimulate enzyme activity.

Stability of lactobacilli encapsulated in various microbial polymers.

Various microbial polymers, namely xanthan gum, gellan gum, pullulan gum and jamilan, were tested as a suitable encapsulating material for Lactobacillus plantarum CRL 1815 and Lactobacillus rhamnosus ATCC 53103. Resulting capsules were also studied for their pH and simulated gastrointestinal conditions tolerance. The morphology of the microcapsules was studied using scanning electron microscopy. pH tolerance was tested at pH 2.0, 3.5, 5.0 and 6.5 over a 6h incubation period. Simulated gastrointestinal conditions were assayed with simulated gastric and pancreatic juices and simulated bile over a 24h incubation period. Suspensions of probiotic organisms were used as a control. The results from encapsulation with microbial polymers indicate that mixtures of 1% xanthan gum with 0.75% gellan gum and 1% jamilan with 1% gellan gum were the most suitable for microencapsulation. Results for the pH tolerance tests showed no improvement in the viability of cells in relation to the control, except for pH 2.0 where lactobacilli encapsulated in xanthan:gellan gum (1%:0.75%) prolonged their viability by 6h exposure. Xanthan:gellan gum (1%:0.75%) was the most effective of the encapsulating materials tested in protecting L. plantarum and L. rhamnosus against simulated bile, improving its viability in 1-2 logCFU when compared with control. The results of this study suggest that microbial polymers are an interesting source of encapsulating material that should be taken into account for prospective studies of probiotic encapsulation for oral delivery applications.

Cellular Fatty Acid Composition of Deleya halophila: Effect of Growth Temperature and Salt Concentration

SUMMARY: The cellular fatty acid composition of Deleya halophila, a moderately halophilic bacterium, grown at different temperatures and NaCl concentrations is reported. When the temperature was lowered the amounts of monounsaturated C16:1 and C18:1 fatty acids increased with a corresponding decrease in the amounts of saturated C16:0 and C18:0 fatty acids. Increasing the salt concentration in the medium resulted in an increase of cyclopropane fatty acids, with a concomitant decrease in the monounsaturated fatty acids, suggesting that cyclopropane synthetase is activated or induced by high levels of salt.

Formation of calcium carbonate crystals by moderately halophilic bacteria

Abstract Production of calcium carbonate by moderately halophilic bacteria was investigated. The crystalline structures were identified by x‐ray diffraction analysis. The results showed that the CaCO3 formation was a general phenomenon for moderately halophilic bacteria and the different salt concentrations in the growth medium were an important factor in the characteristics of crystals formed.

Influence of salt concentration on the cellular fatty acid composition of the moderately halophilic bacterium Halomonas salina

The cellular fatty acid composition of Halomonas salina, a moderately halophilic bacterium grown at different salt concentrations, is reported. Fatty acids C16:0 and C18:1 were major components and significant amounts of C16:1, C18:0 and cyc-C19:0 were also detected. The results showed clear chemotaxonomic relationships with recognized members of the genus Halomonas. The salt concentration greatly influenced the fatty acid composition, suggesting activation of cyclopropane synthetase at high levels of salt, since increases in cyclopropane fatty acids with decreases in monounsaturated fatty acids were observed as the salt concentration in the medium rose.

Taxonomic Study of Extreme Halophilic Archaea Isolated from the “Salar de Atacama”, Chile

A large number of halophilic bacteria were isolated in 1984-1992 from the Atacama Saltern (North of Chile). For this study 82 strains of extreme halophilic archaea were selected. The characterization was performed by using the phenotypic characters including morphological, physiological, biochemical, nutritional and antimicrobial susceptibility test. The results, together with those from reference strains, were subjected to numerical analysis, using the Simple Matching (S(SM)) coefficient and clustered by the unweighted pair group method of association (UPGMA). Fifteen phena were obtained at an 70% similarity level. The results obtained reveal a high diversity among the halophilic archaea isolated. Representative strains from the phena were chosen to determine their DNA base composition and the percentage of DNA-DNA similarity compared to reference strains. The 16S rRNA studies showed that some of these strains constitutes a new taxa of extreme halophilic archaea.