Final Report on the Safety Assessment of Maleic Acid1

Synthesis and characterization of novel guar gum based waste material derived nanocomposite for effective removal of hexabromocyclododecane and lindane

Herein, efficient degradation of hexabromocyclododecane (HBCD) and Lindane, a persistent organic pollutant using guar gum based calcium oxide doped silicon dioxide (GG-CaO@SiO2) has been reported. The nanocomposite was prepared by waste egg shell (CaO) and rice husk (SiO2) was well characterized. The maximum degradation of HBCD and Lindane were observed at 8 mg catalyst loading, neutral pH, and 2 mg L-1 of pollutant amount. The photocatalytic performance of GG-CaO@SiO2 for HBCD and Lindane photodegradation was evaluated, and it was found that the rate constant increased in the order of GG-CaO@SiO2 > CaO@SiO2 > GG. The polymeric GG-CaO@SiO2 nanocomposite showed maximum removal of both pollutants due to higher surface area (70 m2 g-1) and synergistic interactions among GG moieties. It achieved HBCD and Lindane elimination rates of 94 % and 90 % by photo-adsorptive degradation within 150 min. Meanwhile, the leaching of HBCD from expanded polystyrene (EPS) materials (0.14 ± 0.05 ppm) underwater with different time intervals and degradation of leachate HBCD were also assessed. The eradication of the pollutant manifested first-order kinetics, with the Langmuir adsorption. LC-MS analysis confirmed that GG-CaO@SiO2 effectively breaks down complex structure toxic pollutants into safer metabolites under natural sunlight exposure. The polymeric GG-CaO@SiO2 nanocomposite showed notable reusability up to ten cycle promotes sustainability.

Identification of pyruvic and maleic acid as potential markers for disease activity and prognosis in chronic urticaria

BACKGROUND

Population-based studies have highlighted the link between chronic urticaria (CU) and metabolic syndrome, and metabolic alterations have been revealed in CU. However, to our knowledge, a comprehensive metabolomics study on a large cohort of patients with CU has not been reported.

OBJECTIVE

We sought to explore the underlying metabolic subtypes and novel metabolite biomarkers for CU diagnosis and therapy.

METHODS

Plasma samples from 80 patients with CU and 82 healthy controls were collected for metabolomics quantification and bioinformatics analysis. Another independent cohort consisting of 144 patients with CU was studied to validate the findings. Bone marrow-derived mast cells and mice with IgE-induced passive cutaneous anaphylaxis were used for in vitro and in vivo experiments, respectively.

RESULTS

We observed clear metabolome differences between CU patients and healthy controls. Meanwhile, differential metabolites N6-acetyl-l-lysine, l-aspartate, maleic acid, and pyruvic acid were used to construct random forest classifiers and achieved area under receiver operating characteristic curve values greater than 0.85, suggesting their potential as diagnostic biomarkers of CU. More importantly, by exploring the underlying metabolic subtypes of CU, we found that the low abundance of pyruvic acid and maleic acid was significantly related to the activity of CU, poor efficacy of second-generation H1 antihistamines, and short relapse-free time. The results were validated in the independent cohort. Moreover, supplementation with pyruvate or maleate could significantly attenuate IgE-mediated mast cell activation in vitro and in vivo.

CONCLUSIONS

Plasma pyruvic acid and maleic acid may be effective biomarkers for predicting disease activity, therapeutic efficacy, and prognosis for patients with CU.

Extending the shikimate pathway for microbial production of maleate from glycerol in engineered Escherichia coli

Maleate is one of the most important unsaturated four-carbon dicarboxylic acids. It serves as an attractive building block in cosmetic, polymer, and pharmaceutical industries. Currently, industrial production of maleate relies mainly on chemical synthesis using benzene or butane as the starting materials under high temperature, which suffers from strict reaction conditions and low product yield. Here, we propose a novel biosynthetic pathway for maleate production in engineered Escherichia coli. We screened a superior salicylate 5-hydroxylase that can catalyze hydroxylation of salicylate into gentisate with high conversion rate. Then, introduction of salicylate biosynthetic pathway and gentisate ring cleavage pathway allowed the synthesis of maleate from glycerol. Further optimizations including enhancement of precursors supply, disruption of competing pathways, and construction of a pyruvate recycling system, boosted maleate titer to 2.4 ± 0.1 g/L in shake flask experiments. Subsequent scale-up biosynthesis of maleate in a 3-L bioreactor under fed-batch culture conditions enabled the production of 14.5 g/L of maleate, indicating a 268-fold improvement compared with the titer generated by the wildtype E. coli strain carrying the entire maleate biosynthetic pathway. This study provided a promising microbial platform for industrial level synthesis of maleate, and demonstrated the highest titer of maleate production in microorganisms so far.

Metabolomes and Lipidomes of the Infective Stages of the Gastrointestinal nematodes, Nippostrongylus brasiliensis and Trichuris muris

Soil-transmitted helminths, including hookworms and whipworms, infect billions of people worldwide. Their capacity to penetrate and migrate through their hosts’ tissues is influenced by the suite of molecules produced by the infective developmental stages. To facilitate a better understanding of the immunobiology and pathogenicity of human hookworms and whipworms, we investigated the metabolomes of the infective stage of Nippostrongylus brasiliensis third-stage larvae (L3) which penetrate the skin and Trichuris muris eggs which are orally ingested, using untargeted liquid chromatography-mass spectrometry (LC-MS). We identified 55 polar metabolites through Metabolomics Standard Initiative level-1 (MSI-I) identification from N. brasiliensis and T. muris infective stages, out of which seven were unique to excretory/secretory products (ESPs) of N. brasiliensis L3. Amino acids were a principal constituent (33 amino acids). Additionally, we identified 350 putative lipids, out of which 28 (all known lipids) were unique to N. brasiliensis L3 somatic extract and four to T. muris embryonated egg somatic extract. Glycerophospholipids and glycerolipids were the major lipid groups. The catalogue of metabolites identified in this study shed light on the biology, and possible therapeutic and diagnostic targets for the treatment of these critical infectious pathogens. Moreover, with the growing body of literature on the therapeutic utility of helminth ESPs for treating inflammatory diseases, a role for metabolites is likely but has received little attention thus far.

Profiling transcriptomes of human SH-SY5Y neuroblastoma cells exposed to maleic acid

Background

Maleic acid is a multi-functional chemical widely used in the field of industrial chemistry for producing food additives and food contact materials. As maleic acid may contaminate food by the release from food packages or intentional addition, it raises the concern about the effects of excessive dietary exposure to maleic acid on human health. However, the influence of maleic acid on human health has not been thoroughly studied. In silico toxicogenomics approaches have found the association between maleic acid and nervous system disease in human. The aim of this study is to experimentally explore the effects of maleic acid on human neuronal cells.

Methods

A microarray-based transcriptome profiling was performed to offer a better understanding of the effects of maleic acid on human health. Gene expression profiles of human neuroblastoma SH-SY5Y cells exposed to three concentrations of maleic acid (10, 50, and 100 μM) for 24 h were analyzed. Genes which were differentially expressed in dose-dependent manners were identified and further analyzed with an enrichment analysis. The expression profile of selected genes related to the inferred functional changes was validated using quantitative polymerase chain reaction (qPCR). Specific fluorescence probes were applied to observe the inferred functional changes in maleic acid-treated neuronal cells.

Results

A total of 316 differentially expressed genes (141 upregulated and 175 downregulated) were identified in response to the treatment of maleic acid. The enrichment analysis showed that DNA binding and metal ion binding were the significant molecular functions (MFs) of the neuronal cells affected by maleic acid. Maleic acid exposure decreased the expression of genes associated with calcium and thiol levels of the cells in a dose-dependent manner. The levels of intracellular calcium and thiol levels were also affected by maleic acid dose-dependent.

Discussion

The exposure to maleic acid is found to decrease the cellular calcium and thiol levels in human neuronal cells at both transcriptional and functional levels. This study reported the first transcriptomic profiling of human neuronal cells treated with maleic acid. It is also the first experimental validation of chemical effects predicted by in silico toxicogenomics approaches. The proposed approach may be useful in understanding the potential effects of other poorly characterized chemicals on human health.

Assembly of Layered Monetite-Chitosan Nanocomposite and Its Transition to Organized Hydroxyapatite

Bioinspired synthesis of hierarchically structured calcium phosphate (CaP) material is a highly promising strategy for developing improved bone substitute materials. However, synthesis of CaP materials with outstanding mechanical properties still remains an ongoing challenge. Inspired by the formation of lamellar structure in nacre, we designed an organic matrix composed of chitosan and cis-butenediolic acid (maleic acid, MAc) that could assemble into a layered complex and further guide the mineralization of monetite crystals, resulting in the formation of organized and parallel arrays of monetite platelets with a brick-and-mortar structure. Using the layered monetite-chitosan composite as a precursor, we were able to synthesize hydroxyapatite (HAp) with multiscale hierarchically ordered structure via a topotactic phase transformation process. On the nanoscale, needlelike HAp crystallites assembled into organized bundles that aligned to form highly oriented plates on the microscale. On the large-scale level, these plates with different crystal orientations were stacked together to form a layered structure. The organized structures and composite feature yielded CaP materials with improved mechanical properties close to those of bone. Our study introduces a biomimetic approach that may be practical for the design of advanced, mechanically robust materials for biomedical applications.

ChemDIS: a chemical-disease inference system based on chemical-protein interactions

Background

The characterization of toxicities associated with environmental and industrial chemicals is required for risk assessment. However, we lack the toxicological data for a large portion of chemicals due to the high cost of experiments for a huge number of chemicals. The development of computational methods for identifying potential risks associated with chemicals is desirable for generating testable hypothesis to accelerate the hazard identification process.

Results

A chemical–disease inference system named ChemDIS was developed to facilitate hazard identification for chemicals. The chemical–protein interactions from a large database STITCH and protein–disease relationship from disease ontology and disease ontology lite were utilized for chemical–protein–disease inferences. Tools with user-friendly interfaces for enrichment analysis of functions, pathways and diseases were implemented and integrated into ChemDIS. An analysis on maleic acid and sibutramine showed that ChemDIS could be a useful tool for the identification of potential functions, pathways and diseases affected by poorly characterized chemicals.

Conclusions

ChemDIS is an integrated chemical–disease inference system for poorly characterized chemicals with potentially affected functions and pathways for experimental validation. ChemDIS server is freely accessible at http://cwtung.kmu.edu.tw/chemdis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13321-015-0077-3) contains supplementary material, which is available to authorized users.