Performance evaluation of a two-phase anaerobic digestion process of synthetic domestic wastewater at ambient temperature

Organophosphate toxicity: updates of malathion potential toxic effects in mammals and potential treatments

Organophosphorus insecticides toxicity is still considered a major global health problem. Malathion is one of the most commonly used organophosphates nowadays, as being considered to possess relatively low toxicity compared with other organophosphates. However, widespread use may lead to excessive exposure from multiple sources. Mechanisms of MAL toxicity include inhibition of acetylcholinesterase enzyme, change of oxidants/antioxidants balance, DNA damage, and facilitation of apoptotic cell damage. Exposure to malathion has been associated with different toxicities that nearly affect every single organ in our bodies, with CNS toxicity being the most well documented. Malathion toxic effects on liver, kidney, testis, ovaries, lung, pancreas, and blood were also reported. Moreover, malathion was considered as a genotoxic and carcinogenic chemical compound. Evidence exists for adverse effects associated with prenatal and postnatal exposure in both animals and humans. This review summarizes the toxic data available about malathion in mammals and discusses new potential therapeutic modalities, with the aim to highlight the importance of increasing awareness about its potential risk and reevaluation of the allowed daily exposure level.

Less biomass and intracellular glutamate in anodic biofilms lead to efficient electricity generation by microbial fuel cells

BACKGROUND

Using a microbial fuel cell (MFC), we observed that a complex microbial community decomposed starch and transferred electrons to a graphite felt anode to generate current. In spite of the same reactor configuration, inoculum, substrate, temperature, and pH, MFCs produced different current and power density. To understand which factor(s) affected electricity generation, here, we analyzed a complex microbial community in an anodic biofilm and fermentation broth using Illumina MiSeq sequencing and metabolomics.

RESULTS

Microbial biomass on the anode was lower in MFCs generating more electricity (0.09-0.16 mg cm^-2-anode) than in those generating less electricity (0.60-2.80 mg cm^-2-anode), while being equal (3890-4196 mg L^-1-broth) in the fermentation broth over the same operational period. Chemical oxygen demand removal and acetate concentration were also similar in fermentation broths. MFCs generating more electricity had relatively more exoelectrogenic bacteria, such as Geobacter sp., but fewer acetate-utilizing Methanosarcina sp. and/or Lactococcus sp. in anodic biofilms. Accordingly, anodic biofilms generating more electricity presented higher levels of most intracellular metabolites related to the tricarboxylic acid cycle and a higher intracellular ATP/ADP ratio, but a lower intracellular NADH/NAD⁺ ratio. Moreover, the level of intracellular glutamate, an essential metabolite for microbial anabolic reactions, correlated negatively with current density.

CONCLUSION

Microbial growth on the anode and intracellular glutamate levels negatively affect electricity generation by MFCs. Reduced formation of anodic biofilm, in which intracellular glutamate concentration is 33.9 μmol g-cell^-1 or less, favors the growth of acetate-utilizing Geobacter sp. on the anode and improves current generation.

Comparative metabolic state of microflora on the surface of the anode electrode in a microbial fuel cell operated at different pH conditions

The metabolic state of microflora (mixed microbial cultures) in microbial fuel cells (MFCs) is currently unclear. Metabolomic analyses were conducted of microflora growing on the anodic electrodes of MFCs operated at pH 7.0, 5.5, or 4.0 and utilizing starch as the major carbon substrate. A much higher current was produced at pH 7.0 than at pH 5.5 and 4.0, correlating with an increased population ratio of Geobacter species to the total bacteria growing on the electrode. Most intracellular metabolites related to the tricarboxylic acid (TCA) cycle were present at a higher level at pH 7.0 than at pH 5.5 and 4.0, and the levels of metabolites correlated well with the obtained current densities. A high intracellular adenosine triphosphate (ATP)/adenosine diphosphate (ADP) ratio at pH 7.0, compared to at pH 5.5 and 4.0, likewise supported current production. Overall, the metabolomic analyses demonstrated that activation of the TCA cycle and increased ATP generation are critical parameters for electricity generation by microflora.

Assessment of the anaerobic acidogenesis of wet olive cake from a two-phase olive oil mill

A study of the anaerobic acidogenesis of wet olive cake or olive mill solid waste (OMSW) from the two-phase olive oil mill industry was carried out. Eight different hydraulic retention times (HRTs) ranging from 50.0-10.7 days were studied. An increase of 935.7 % in total volatile fatty acids (VFA) over the initial acidic concentration in the OMSW (1.4 g L(-1) expressed as acetic acid) was achieved. The results showed a maximum total VFA generation rate of 5.05 g COD L(-1)d(-1), this rate being achieved at the same hydraulic retention time as the maximum acetic acid production (8.2 g L(-1)) and as the maximum acidification degree (34.4 %).