The main purpose of this work was to isolate and characterize lactic acid bacteria (LAB) strains to be used for biomass production using a whey-based medium supplemented with an ammonium salt and with very low levels of yeast extract (0.25 g/L). Five strains of LAB were isolated from naturally soured milk after enrichment in whey-based medium. One bacterial isolate, designated MNM2, exhibited a remarkable capability to utilize whey lactose and give a high biomass yield on lactose. This strain was identified as Lactobacillus casei by its 16S rDNA sequence. A kinetic study of cell growth, lactose consumption, and titratable acidity production of this bacterial strain was performed in a bioreactor. The biomass yield on lactose, the percentage of lactose consumption, and the maximum increase in cell mass obtained in the bioreactor were 0.165 g of biomass/g of lactose, 100%, and 2.0 g/L, respectively, which were 1.44, 1.11, and 2.35 times higher than those found in flask cultures. The results suggest that it is possible to produce LAB biomass from a whey-based medium supplemented with minimal amounts of yeast extract.

The symbiotic relationship between native microbiota and their hosts probably is a key factor in animal survival. In this study, the relationships of Pseudomonas spp. strains with specific biomarkers of exposure to polycyclic aromatic hydrocarbons (PAHs) in wild fish Chirostoma jordani, as well as the capacity of these bacteria to biotransform PAHs were evaluated. The activity of the naphthalene dioxygenase system of the bacteria exposed to 0.1, 1.0 and 10 µg/L of PAHs was higher than the mean isoform 1A1 (CYP1A1) of the wild fish, particularly bacterial species related to Pseudomonas spp. However, the epoxide hydrolase activity of the strains was lower in all cases compared to the fish. Glutathione S-transferase (GST) activity of the bacterial strains was lower than in the liver, but higher than in viscera of C. jordani. Using redundancy analysis, two differential patterns were found: (i) CYP1A1 activity of fish was induced by naphthalene and anthracene water levels independently of sampling season and lakes monitored, and (ii) the unidentified strain of the Pseudomonas genus biotransforms the endogenous levels of benzo[a]pyrene, benzo[k]fluoranthene and indeno[1,2,3-cd]pyrene in the fish allowing the hydroxylated metabolites to conjugate with glutathione through GST activity of the fish. Palabras clave: CYP 1A1, epóxido hidrolasa, GST, HAP, oxidasas, sistema NDO RESUMEN Las relaciones simbióticas entre la microbiota nativa y sus hospederos probablemente son un factor clave en la supervivencia animal. En el presente estudio se evaluaron las relaciones de cepas de Pseudomonas spp. con biomarcadores específicos de exposición a hidrocarburos aromáticos policíclicos (HAP) en Chirostoma jordani silvestre, así como la capacidad de estas bacterias para biotransformar HAP. La actividad del sistema de naftalen-dioxigenasa de las bacterias expuestas a 0,1, 1,0 y 10 μg/L de HAP fue superior al promedio de la isoforma 1A1 (CYP1A1) en los peces, particularmente cepas relacionadas con especies de Pseudomonas spp. Sin embargo, la actividad de la epóxido hidrolasa de las bacterias fue menor en comparación con los peces. La catálisis de la glutatión-S-transferasa (GST) de las cepas bacterianas fue menor que en

Goodea gracilis is an endemic fish that only habitats in some water bodies of Central Mexico that are contaminated with cyanobacteria-producing microcystins (MC); however, a lack of information on this topic prevails. With the aim to generate the first approximation about the physiological changes elicited by cyanobacterium that produce MC congeners in this fish species, specimens born in the laboratory was exposed for 96 h to cell densities of 572.5, 1145, 2290, 4580, and 9160 × 10(6) cells of Microcystis aeruginosa strain LB85/L, and a set of novel endpoint related to hepatic gluconeogenesis (ADH/LDH) and pro-oxidant forces O2., H2 O2 ) in addition to biomarkers of oxidative damage and antioxidant response was evaluated in the liver. Results suggest that high inhibition of protein serine/threonine phosphatase (PP) may trigger many metabolic processes, such as those related to hepatic gluconeogenesis (ADH/LDH) and pro-oxidant O2⋅, H2 O2 , TBARS, ROOH, RC=O) as well as antioxidant (SOD, CAT, GPx) response to oxidative stress. Particularly, we observed that inhibition of LDH and PP, and H2 O2 increase and TBARS production were the key damages induced by high densities of M. aeruginosa. However, changes between aerobic and anaerobic metabolism related with ROS metabolism and ADH/LDH balance are apparently an acclimation of this fish species to exposure to cyanobacteria or their MCs. Fish species living in environments potentially contaminated with cyanobacteria or their MCs possess mechanisms of acclimation that allow them to offset the damage induced, even in the case of fish that have never been exposed to MCs.

Halomethanes (HM) can be immunotoxic in mammals; however, in the fish immune system HM effects are unknown. In the current study, we evaluated the mitochondrial activity (MA) by MTT, induction of apoptosis by SubG0 technique and quantified serum ROS concentration (O2. and H2O2) and ROS production in PBMC of Cyprinus carpio carpio treated i.p. with CH2Cl2, CHCl3 and BrCHCl2 (0.004-40.0 mg/kg) for 96 h. Positive controls were recombinant heat shock protein of 60 kDa (rHSP60 kDa) of Klebsiella pneumoniae and its LPS. In addition, for in vitro PBMC cultures, two culture media and two sources of sera were tested. Both positive controls increased the MA more than 4-fold as well as the production of O2. (26-fold) and H2O2 (5-fold) compared to their controls. HM induced different effects on MA, ROS production and an induction of apoptosis, depending on the chlorination patterns and the dose; however, a systemic damage prevails. To fish treated with CH2Cl2, the apoptosis was related with serum ROS concentration and with MA. In contrast, in fish dosed with CHCl3 relationships were not found, deducing a systemic damage. However, in fish treated with BrCHCl2, serum O2. concentration and in vitro ROS generation performed by PBMC were involved in the induction of apoptosis of these cells but not with MA suggesting also immunotoxic effects. The current study demonstrated that HMs are immunomodulators increasing an acute inflammatory response and that rHSP60kDA of K. pneumoniae and its LPS are appropriate antigens to assess the immune response of C. c. carpio.

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