Chain Carboxylic Acids Research Articles

Co-fermenting lactic acid and glucose towards caproic acid production

The functional role of lactate (HLac), as a co-substrate along with glucose (Glu) as well as an electron donor for the synthesis of caproic acid (HCa), a medium chain fatty acid (MCFAs) was studied. A varied HLac and Glu ratios were thus investigated in fed-batch anaerobic reactors (R1–R5) operated at pH 6 with a heat-treated anaerobic consortium. R1 and R5 were noted as controls and operated with sole Glu and HLac, respectively. Strategically, ethanol (HEth) was additionally supplemented as co-electron donor after the production of short chain carboxylic acids (SCCAs) for chain elongation in all the reactors. The reactor operated with HLac and Glu in a ratio of 0.25:0.75 (1.25 g/L (HLac) and 3.75 g/L (Glu)) showed the highest HCa production of 1.86 g/L. R5 operated with solely HLac yielded propionic acid (HPr) as the major product which further led to the higher valeric acid (HVa) production of 1.1 g/L within the reactor. Butyric acid (HBu) was observed in R1, which used Glu as carbon source alone indicating the importance of HLac as electron co-donor. Clostridium observed as the most dominant genera in shotgun metagenome sequencing in R2 and R3, the reactors that produced the highest HCa in comparison to other studied reactors. The study thus provided insight into the importance of substrate and electron donor and their supplementation strategies during the production of MCFAs.

Advances in Electricity-Steering Organic Waste Bio-Valorization for Medium Chain Carboxylic Acids Production

Medium chain carboxylic acids (MCCAs, e.g., caproic acid, caprylic acid, etc.) with 6–12 carbon atoms are valuable platform chemicals produced from organic waste via microbial chain elongation metabolism named as reversed β-oxidation and fatty acid-biosynthesis cyclical pathway. Recently, many articles reported that electricity could not only serve as the external electron donor and provide the reduction equivalent required for chain elongation but also regulate the microbiome structure and metabolic behaviors to promote MCCAs formation. Electricity-steering MCCAs bioproduction has become an appealing technique to valorize low-value organic waste, paving an alternative pathway for net-zero carbon emission energy systems and sustainable socio-economic development. However, the MCCAs’ bioproduction from organic waste steered by electric field has not been comprehensively reviewed. From a systematical analysis of publicly available literature, we first covered the basic working principle, fermentation architecture, functional microflora, and metabolic pathway of MCCAs production driven by electricity. The strategies of substrate modulation, applied voltage/current regulation, electrode optimization, and microbial cooperation and stimulation for boosting electricity-driven MCCAs bioproduction are then scrutinized and extensively discussed. Ultimately, the pressing knowledge gaps and the potential path forward are proposed to provide pointers for consistently higher MCCAs yield and the transition from laboratory to market.

Enhanced degradation of sulfamethazine in FeCeOx Fenton-like system by tea polyphenols as reducing agents: Performance, mechanism and pathway

In this study, we constructed a Fenton-like system with FeCeOx nanocomposite, tea polyphenols (TP) and H2O2 for the degradation of sulfamethazine (SMT). Compared with other reducing agents (RAs), the addition of TP had a strong promoting effect on SMT degradation of FeCeOx/H2O2/RAs system, then FeCeOx/H2O2/TP system could realize the complete degradation of SMT within 90 min under optimized conditions of 150 mg·L−1 of catalyst dosage, 2.12 mmol·L−1 of H2O2 concentration, 115 mg·L−1 of TP dosage and 5.2 of initial pH. The main active species in FeCeOx/H2O2/TP system and their corresponding contributions to the SMT degradation were ranked as following: ∙OH (52.5%) > 1O2 (31.9%) > ∙O2- (15.6%). The reduction mechanism (heterogeneous catalysis) and chelation mechanism (homogeneous catalysis) of FeCeOx/H2O2/TP system were proposed. The addition of TP not only achieved the circulation of Fe/Ce species and the formation of oxygen vacancies on the catalyst surface, but also could accelerated the formation of various chelate structure in solution, which both contributed to the generation of active species. SMT was mineralized into CO2, H2O2 and some short chain carboxylic acids through five degradation pathways. Finally, FeCeOx/H2O2/TP system exhibited favorable degradation rate (>90%) towards SMT after six recycling times, and it could work effectively in different water sources. This study provided a new insight into Fenton-like process for improving pollutant degradation.

Fabrication of Superhydrophobic Surface on Anodized Aluminum Through a Wet-Chemical Route

Fabrication of superhydrophobic surfaces on anodized aluminum substrates by wet-chemical grafting using cost-effective chemicals through a simple immersion process is described in this work. Formation of formate-alumoxane is possible by treating the anodized and sealed aluminum substrate with formic acid at around 50 °C. On treatment with sodium salts of higher-order carboxylic acids (stearic acid, lauric acid, and palmitic acid), the formate ions are replaced by higher-order carboxylates. A possible bonding mechanism of the longer chain carboxylic acids with aluminium surfaces has been suggested based on IRRAS and XPS studies. The as-prepared superhydrophobic aluminum substrates exhibited a static water contact angle of up to 167° with a sliding angle not higher than 6°, with decent resistance against abrasion in addition to good UV, environmental and thermal stabilities. Aluminium substrates of any size, shape and surface finish can be easily rendered robust and superhydrophobic without the use of expensive chemicals and sophisticated machinery.

Effect of nanoparticles and nanosheets on improving the oil/water interface performance of surfactants in enhancing oil recovery: A comparative study by molecular simulation

In recent years, nanoparticles have become the most potential enhanced oil recovery technology because of their unique small size effect and specific surface area effect. With the research and application of graphene and its derivative materials, nanosheets are one of the research hotspots of nanomaterials for enhanced surfactant flooding. However, as far as we know, the molecular simulation comparison of nanoparticles and nanosheets to enhance the performance of surfactants has not been reported so far. Therefore, in this paper, we constructed nano-SiO2 particles grafted with hydroxyl and pentyl alkane activator, graphene nanosheets grafted with carboxylic acid chain and pentyl alkane activator for the first time. On this basis, the interfacial tension, interfacial density, interfacial generation energy and radial distribution function were analyzed by molecular dynamics simulation. The results show that nanoparticles and nanosheets have synergistic effect with amphoteric surfactant dodecyl dimethyl aminoethyl lactone (BS-12). The synergistic effect of nanosheets and BS-12 was stronger after carboxylic acid chain and pentyl alkane activator are grafted on the surface of nanosheets. The interfacial tension of n-dodecane/water could be reduced to 13.58 mN/m after the modified nanosheets are compounded with BS-12. The interfacial tension of n-dodecane/water could be reduced to 4.15 mN/m by the modified nanosheets are compounded with BS-12, and the ability of reducing the interfacial tension between oil and water is significantly improved. The calculation of n-dodecane/water interface thickness and interface formation energy showed that compared with the modified nanoparticles and BS-12 compound system, the interface thickness of the modified nanosheets and BS-12 compound system increased by 9.24%, and the interface formation energy increased by 17.85%. In addition, the results of radial distribution function analysis also demonstrated that the modified nanosheets had strong hydration with water molecules after being compounded with BS-12. The results of this work can provide new ideas for further research on the synergistic effect of surfactants and nanomaterials, as well as the development of oil displacement technology based on surfactants/nanomaterials.

Protic ionic liquids based on fatty acids: A mixture of ionic and non-ionic molecules

Fatty acids are long chain carboxylic acids naturally and abundantly found in oils and fats; therefore, they are interesting candidates for protic ionic liquids (PILs) synthesis. Mixtures of carboxylic acids and amines should lead to intermediate proton transfer from the acid to the amine to form PILs, with both ionic molecules (PIL) and non-ionic molecules observed in these mixtures, depending on the nature of the amine. This work studied the physicochemical properties of mixtures between fatty acids and amines, with phase transitions, thermal stability, viscosity, solvation (Kamlet-Taft parameters) and proton transfer evaluated. Our results show that like other carboxylic acids the proton transfer is highly dependent on the structure of the amine, being much higher for primary amines than for tertiary amines. Also, hydroxyl groups on tertiary amines increase the proton transfer. The extent of the proton transfer strongly influences the physicochemical properties of the mixtures, where a larger proton transfer leads to a higher melting point and higher viscosity. Also, mixtures based on highly volatile amines decomposed at low temperatures even when a high degree of proton transfer was observed. Surprisingly, mixtures based on butylamine or triethylamine exhibited high hydrogen bond acceptor capacity and low dipolarity-polarizability which is an unusual characteristics of ionic liquids, potentially opening new solvent application space for ionic liquids.

Regulation on C2-C8 carboxylic acid biosynthesis from anaerobic CO2 fermentation.

Bioconversion of CO2 into liquid fuels or chemicals, preferred medium chain carboxylic acids (caproic and caprylic acid), is an attractive CO2 utilization technology. The present study aims to investigate the effects of different ratios of H2/CO2 on regulating the distribution of C2-C8 carboxylic acid products, while the headspace pressure of 1.5bar was set to amplify the effect of different ratios. The H2/CO2 ratio of 4:1 was more suitable for preparing acetic acid, where the highest acetic acid yield was 17.5g/L. And the H2/CO2 ratio of 2:1 showed excellent chain elongation ability with the highest n-caprylic yield of 2.4g/L. Additionally, the actual H2/CO2 ratios of 4:1 reactors were higher than that in 2:1 may be course chain elongation often accompanied by H2 production. The 16S rRNA genes analysis shows that the genus Terrisporobacter and Coriobacteriales may be related to acetic acid production enriched in H2/CO2 ratio 4:1 reactors, and the genus Clostridium and Paenibacillaceae may associate with the chain elongation pathway were enriched in H2/CO2 ratio 2:1 reactors.

Liquid-liquid equilibrium experiment and mechanism analysis of menthol-based deep eutectic solvents extraction for separation of fuel additive tert-butanol

Deep eutectic solvents (DESs) were synthesized using menthol as hydrogen bond acceptor (HBA) and different carbon chain carboxylic acids as hydrogen bond donors (HBD). The liquid equilibrium (LLE) experiment was used to determine the distribution coefficient (β) and slectivity (S) at standard atmospheric pressure and temperature. The effect of DESs on the separation efficiency was discussed by changing the proportion. Non-random two fluid (NRTL) model was used to correlate the experimental data. The molecular dynamics (MD) simulation method was used to investigate the micro mechanism of the extraction process. The results show van der Waals force plays a leading role in the interaction between solvents and tert-butyl alcohol (TBA) and week force with water. Compared with experimental and simulation results, the interaction between DESs and TBA would also be affected by the change of the number of HBD carbon chains, and DESs with decanoic acid as HBD has the best separation effect, which verifies the feasibility of separating high alcohol compounds from water by DESs and then treating them by DESs.

Thermophilic caproic acid production from grass juice by sugar-based chain elongation

Medium chain carboxylic acids (MCCA) such as caproic acid have a plethora of applications, ranging from food additives to bioplastics. MCCA can be produced via microbial chain elongation using waste and side-streams as substrates, a process that can be more sustainable than conventional production routes. Most chain elongation studies have focused on mesophilic conditions, with only two recent studies hinting at the possibility of thermophilic chain elongation, but a systematic study of its mechanisms is lacking. Here, we investigated thermophilic chain elongation from grass juice, to understand the effect of key operational parameters (pH, temperature, substrate) on the process performance and to establish the key microbial genera and their role in the system. The genus Caproiciproducens was identified as responsible for thermophilic chain elongation, and caproic acid production was most favorable at pH 6.0 and 50 °C among the conditions tested, reaching an average concentration of 3.4 g/L. Batch experiments showed that the substrate for caproic acid production were glucose and xylose, while lactic acid led to the production of only butyric acid. Fed-batch experiments showed that substrate availability and the presence of caproic acid in the system play a major role in shaping the profile of thermophilic chain elongation. The increase of the total sugar concentration by glucose addition (without changing the organic load) during continuous operation led to a microbial community dominated (75 %) by Caproiciproducens and increased by 76 % the final average caproic acid concentration to 6.0 g/L (13 gCOD/L) which represented 32 % (g/g) of the total carboxylic acids. The highest concentration achieved was 7.2 g/L (day 197) which is the highest concentration reported under thermophilic conditions thus far. The results of this work pave the way to the potential development of thermophilic systems for upgrading various underexplored abundant and cheap sugar-rich side-streams to caproic acid.

The Effect of Short Chain Carboxylic Acids as Additives on the Crystallization of Methylammonium Lead Triiodide (MAPI)

Due to their exceptional properties, the study of hybrid perovskite (HyP) structures and applications dominate current photovoltaic prospects. Methylammonium lead tri-iodide perovskite (MAPI) is the model compound of the HyP class of materials that, in a few years, achieved, in photovoltaics, a power conversion efficiency of 25%. The attention on HyP has recently moved to large single crystals as emerging candidates for photovoltaic application because of their improved stability and optoelectronic properties compared to polycrystalline films. To control the quality and symmetry of the large MAPI single crystals, we proposed an original method that consisted of adding short-chain carboxylic acids to the inverse temperature crystallization (ICT) of MAPI in γ-butyrolactone (GBL). The crystals were characterized by single-crystal X-ray diffraction (SC-XRD), X-ray powder diffraction (XRPD) and Raman spectroscopy. Based on SC-XRD analysis, MAPI crystals grown using acetic and trifluoroacetic acids adopt a tetragonal symmetry “I4cm”. MAPI grown in the presence of formic acid turned out to crystallize in the orthorhombic “Fmmm” space group demonstrating the acid’s effect on the crystallization of MAPI.

Mesoporous aluminas synthesis using carboxylic acids to enhance performance in CO2 adsorption

This work evaluated for the first time the effect of carbon chain size of different carboxylic acids (stearic and caprylic acid) and crystallization temperatures (60, 120, and 180 °C) on the structural, textural, morphological, basic, and mechanism properties of reaction in the synthesis of mesoporous aluminas (meso-Al2O3). Regarding the structure-directing agents (SDA) traditionally used in the synthesis of meso-Al2O3 (i.g. strong acids, strong bases, and synthetic polymers), carboxylic acids are non-toxic, biodegradable compounds of low commercial value, and can be obtained from renewable sources. The physical-chemical characterizations performed, including low and high-angle X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermal analysis (TG/DTG), nitrogen adsorption-desorption, temperature-programmed desorption of carbon dioxide (CO2-TPD), scanning electron microscopy (SEM), and transmission (TEM), confirmed the formation of mesostructured γ-Al2O3. No pore organization was observed, but a system of interconnected channels was provided by the wormhole-like structure. Mesoporous aluminas synthesized at 180 °C showed an increase in structural, textural (higher of 68 % in pore volume and 36% in pore diameter), and basic properties (around 19 %) about materials synthesized at 60 °C. This can be attributed to the increased degree of coordination of the carboxylic acid with aluminum during the hydrolysis-condensation reactions. Furthermore, stearic acid (longer carbon chain carboxylic acid) tends to bend during micellar aggregation, leading to pore sizes 33% smaller than caprylic acid (shorter carbon chain acid). Therefore, the best condition for meso-Al2O3 synthesis was obtained at 180 °C and using caprylic acid (CAP-180 °C) as SDA. The results of CO2 adsorption showed that all materials correlate better with the pseudo-first order model in the entire temperature range studied (10 – 50 °C), suggesting that diffusion through the interface gas-solid (external diffusion) is the limiting step of the adsorption process. The adsorbent CAP-180 °C showed high adsorption capacity (around 134.45 mgCO2/gads at 10 °C under atmospheric pressure) and elevated stability after eight cycles of adsorption-desorption, reaching adsorption capacity superior to other meso-Al2O3.

Highly selective butyric acid production by coupled acidogenesis and ion substitution electrodialysis

Selective production of carboxylic acids (CAs) from mixed culture fermentation remains a difficult task in organic waste valorization. Herein, we developed a facile and sustainable carbon loop strategy to regulate the fermentation micro-environment and steer acidogenesis towards selective butyric acid production. This new ion substitution electrodialysis-anaerobic membrane bioreactor (ISED-AnMBR) integrated system demonstrated a high butyric acid production at 11.19 g/L with a mass fraction of 76.05%. In comparison, only 1.04 g/L with a mass fraction of 30.56% was observed in the uncoupled control reactor. The carbon recovery reached a maximum of 96.09% with the assistance of ISED. Inorganic carbon assimilation was believed to be an important contributor, which was verified by 13C isotopic tracing. Microbial community structure shows the dominance of Clostridia (80.16%) in the unique micro-environment (e.g., pH 4.80–5.50) controlled by ISED, which is believed beneficial to the growth of such fermentative bacteria with main products of butyric acid and acetic acid. In addition, the emergence of chain elongators such as Clostridium sensu stricto 12 was observed to have a great influence on butyric acid production. This work provides a new approach to generate tailored longer chain carboxylic acids from organic waste with high titer thus contributing to a circular economy.

Using Au NPs anchored on ZrO2/carbon black toward more efficient H2O2 electrogeneration in flow-by reactor for carbaryl removal in real wastewater

In the present study, we designed a highly efficient catalyst for H2O2 production using gold nanoparticles (Au NPs) anchored on hybrid substrate composed of ZrO2 and Printex L6 carbon (Au-ZrO2/PL6C). The higher selectivity of Au-ZrO2/PL6C (97%) toward H2O2 electrogeneration and its improved activity in terms of ORR onset potential (140 mV for more positive values) compared to Au/PL6C (80%) were attributed to the synergism between Au NPs anchored on ZrO2/PL6C hybrid support. The results obtained from the application of the catalysts for H2O2 generation on gas diffusion electrode (GDE) after 120 min of electrolysis reflected the following order of efficiency: PL6C (∼140 mg L−1) < ZrO2/PL6C (∼235 mg L−1) < Au/PL6C (∼374 mg L−1) < Au-ZrO2/PL6C (∼600 mg L−1). Given that Au-ZrO2/PL6C exhibited the highest catalytic efficiency, this catalyst was employed for the removal of carbaryl (CBR) using different electrochemical advanced oxidation processes. The CBR degradation tests exhibited pseudo first-order kinetics, with the electro-Fenton (EF) and photoelectro-Fenton (PEF) processes recording the fastest removal kinetics (3.5 × 10−2 s−1 and 4.1 × 10−2 s−1, respectively). The PEF process exhibited the highest efficiency in terms of organic by-products mineralization; this was attributed to the additional photodecarboxylation of the Fe(III)-RCOOH complexes by UVC light. The aromatic by-products, short chain carboxylic acids, and ionic nitrogen species produced during the mineralization process contributed to the successful degradation of CBR. Apart from the analysis with synthetic water, the study also analyzed the treatment of urban wastewater spiked with CBR using a pre-pilot flow plant.

Micellar and sub-micellar chromatography with a cocamidopropyl betaine surfactant

We have coated a typical C18 column with the pH cationic charge controllable zwitterionic synthetic surfactant, cocamidopropyl betaine (CAPB), in order to generate a mixed mode reversed phase weak ion exchange column. As determined by the Thomas model, the column has an adsorbed surfactant capacity of 0.557 mmoles. The addition of 8.8 × 10–4 M CAPB to the totally aqueous mobile phase ensured stability of the surfactant on the column and permitted separation of the four component sulfonamide mixture with micellar liquid chromatography (MLC) in under 11 min. Comparatively, with a dilute H2SO4 mobile phase with no CAPB, the separation time for the sulfonamide mixture reached an excessive run time of an hour on the bare C18 chains. With CAPB in the mobile phase (no organic solvent present), a seven component sulfonamide mixture could be separated in less than 45 min. A five component short chain carboxylic acid mixture, separated in 20 min, was used to examine the ion exchange character of the column in pH environments of 2.3 and 4.6. Three phase MLC equilibrium analysis was also done in these pH environments with the sulfa drug and carboxylic acid mixtures to determine partition coefficients. Finally, a quite high molecular weight (70,000) anionic polystyrene sulfonate polymer was characterized by MLC with only CAPB and variable pH mobile phases; the optimal pH was determined to be 5.6. A totally aqueous mobile phase without CAPB was not suitable for profiling this polymer.

The potential of caproate (hexanoate) production using Clostridium kluyveri syntrophic cocultures with Clostridium acetobutylicum or Clostridium saccharolyticum.

Caproate (hexanoate) and other medium-chain fatty acids are valuable platform chemicals produced by processes utilizing petroleum or plant oil. Clostridium kluyveri, growing on short chain alcohols (notably ethanol) and carboxylic acids (such as acetate) is noted for its ability to perform chain elongation to produce 4- to 8-carbon carboxylates. C. kluyveri has been studied in monoculture and coculture conditions, which lead to relatively modest carboxylate titers after long fermentation times. To assess the biosynthetic potential of C. kluyveri for caproate production from sugars through coculture fermentations, in the absence of monoculture data in the literature suitable for our coculture experiments, we first explored C. kluyveri monocultures. Some monocultures achieved caproate titers of 150 to over 200 mM in 40–50 h with a production rate of 7.9 mM/h. Based on that data, we then explored two novel, syntrophic coculture partners for producing caproate from sugars: Clostridium acetobutylicum and Clostridium saccharolyticum. Neither species has been cocultured with C. kluyveri before, and both demonstrate promising results. Our experiments of C. kluyveri monocultures and C. kluyveri—C. saccharolyticum cocultures demonstrate exceptionally high caproate titers (145–200 mM), fast production rates (3.25–8.1 mM/h), and short fermentation times (18–45 h). These results represent the most caproate produced by a C. kluyveri coculture in the shortest known fermentation time. We also explored the possibility of heterologous cell fusion between the coculture pairs similar to the results seen previously in our group with C. acetobutylicum and Clostridium ljungdahlii. Fusion events were observed only in the C. acetobutylicum—C. kluyveri coculture pair, and we offer an explanation for the lack of fusion between C. saccharolyticum and C. kluyveri. This work supports the promise of coculture biotechnology for sustainable production of caproate and other platform chemicals.

Effect of oil chemistry on the performance of low-salinity waterflooding in carbonates: An integrated experimental approach

Chemical enhanced oil recovery (cEOR) relies on the interactions between surface-active components (SACs) of the oil-in-place and injected chemicals to induce favorable physico-chemical changes. This study investigates the effect of oil chemistry on the performance of chemically-tuned waterflooding (CTWF) in carbonate rocks. Coreflood experiments were performed at 90°C using four model oils, each containing a single SAC (acetic acid, decanoic acid, stearic acid or quinoline) to evaluate the effect of oil composition on oil recovery. Complementary characterization techniques including thermal gravimetric analysis (TGA), attenuated total reflectance (ATR-FTIR) and zeta potential (ζ) were used to understand the underlying rock-oil-brine interactions that take place during CTWF, including SAC adsorption to the rock surface, strength of adsorption, partitioning into the brine phase, and electrostatic interactions, respectively. Sessile drop contact angle measurements were also performed to quantify the wetting behavior of the different SACs. Results of this study show that oil chemistry plays a significant role in triggering different oil-brine-rock interactions. Characterization of those interactions is crucial to explain the discrepancies in oil recovery observed in the CTWF literature. In this study, differences in the underlying oil-brine-rock interactions translated into significant variation in oil recovery ranging between 8.9 and 43.9 % after one pore volume injected (PVI). ATR-FTIR results showed that in-situ soap generation was detected for oils with longer chain carboxylic acids, whereas no soaps were observed for oils that have acetic acid or quinoline. Combined with sessile-drop contact angle measurements, a relationship is observed between SAC partitioning into the brine phase and water-wetting behavior. Additionally, TGA measurements suggested that long chain carboxylic acids chemisorb to the rock surface, making wettability alteration to a less oil-wetting state during CTWF more challenging, whereas intermediate chain carboxylic acids only physisorb leading to a more pronounced wettability alteration to a less oil-wetting state, ultimately yielding the highest recovery of ∼49.9 %. Finally, TAN was found to be an insufficient oil descriptor, where oils with the same TAN yielded different CTWF effects. Hence, a more robust oil analysis is crucial for more accurate prediction and modeling of CTWF behavior.

Rapid Detection of Escherichia coli: Optimized Peptide-Polythiophene Interactions Help Reduce Assay Time and Improve Naked-Eye Detection.

Recent improvements in methods for rapid detection of microbial contamination in food and water samples have aided in the development of on-site and point-of-care testing. Early detection, made possible via on-site testing, can help limit the spread of food and waterborne illnesses. Recently, we reported a novel fluorescence-based Omptin-Polythiophene assay (the assay) to detect Escherichia coli in contaminated water samples. The assay targets OmpT─an E. coli outer membrane protease─and exploits the protease's ability to cleave at dibasic sites within a peptide. By combining a peptide substrate optimized for OmpT with a conjugated polythiophene reporter molecule whose optical properties vary upon interaction with the intact or cleaved peptide, we demonstrated the detection of 1-10 CFU/mL and 105 CFU/mL E. coli in 5.5 and 1 h, respectively. In comparison, most microbial detection methods that rely on culturing and plating techniques take anywhere between 8 and 24 h to report their results. Herein we report significant improvements in the assay which include reducing the assay time from an already short 1 h to a mere 10 min for detecting E. coli in highly contaminated samples and augmenting the assay with colorimetric sensing capability for naked eye discernment under normal visible light or under UV-A light. These improvements were made possible by characterizing the optical changes resulting from the interaction of the peptide with five carboxylate-functionalized polythiophene variants carrying different 3- side chain carboxylic acids and by identifying preferential peptide substrates via the screening of ten peptide sequence variants for OmpT activity.

Integration of anaerobic digestion and chain elongation technologies for biogas and carboxylic acids production from cheese whey

Cheese whey (CW) used for the production of various chemicals in different studies, but no studies designed to produce multiple energy in the form of short-chain/medium-chain carboxylic acids, and biohydrogen (H2) using bio-augmentation strategy by integrating the anaerobic digestion and chain elongation technologies. To achieve this, CW and mixed anaerobic bacteria were kept in an anaerobic chamber for 14 d to produce short chain carboxylic acids (SCCA, acetic (C2), propionic (C3), and butyric (C4) acids), and these SCCA were again converted to medium chain carboxylic acids (MCCA) like hexanoic (C6), heptanoic (C7), and octanoic (C8) acids using enriched bacterial culture, which was bio-augmented with Clostridium kluyveri. SCCA, MCCA, and biogas were analyzed with HPLC and GC. Higher amounts of SCCA, i.e., C2 (10 g/L), C4 (8.1 g/L), and MCCA, i.e., C6 (4.8 g/L), were produced. Biohydrogen (H2) existed in the highest proposition (69%) in biogas composition. Results meant that bio-augmentation strategy could be used for the conversion of CW into valuable carboxylic acids and H2, which have high potential in today's market.

Degradation of cefadroxil by photoelectrocatalytic ozonation under visible-light irradiation and single processes

Here, we investigate the degradation of 20 mg L-1 Cefadroxil (CFX) in water using photoelectrocatalytic ozonation (PECO), and compared against its individual processes. A carbon nitrogen-codoped titanium dioxide (CN-TiO2) anode is synthesized using ethylene glycol and ethylenediamine as carbon and nitrogen source, respectively. The X-ray diffraction (XRD) and Scanning Electronic Microscopy (SEM) analysis conducted to this material indicate a crystalline phase anatase with irregular morphology formed on the electrode surface; while the diffuse reflectance spectroscopy (DRS) shows a shift in the photoanode absorbance towards the visible region, unlike undoped TiO2 structure. This behavior results from the inclusion of Carbon and Nitrogen species on the CN-TiO2 electrode in weight percentages of 14.5 and 1.61 wt%, respectively, according to Energy Dispersive Spectroscopy (EDS) analysis. The Cefadroxil (CFX) abatement is monitored UV–Vis spectroscopy, high-performance liquid chromatography (HPLC), and total organic carbon (TOC). All techniques reveal that the highest CFX removal occurs with PECO (Photoelectrocatalytic Ozonation) process, decreasing TOC by 57.6% (96% degradation by HPLC) after 90 min of treatment. The main by-products formed from oxidation with the PECO, PCO (Photocatalytic Ozonation) and O3 (Ozonation) systems were acid species presumably corresponding to short chain carboxylic acids. Finally, the germination of lettuce sativa is carried out in water contaminated with the drug, and compared with water treated by PECO and PCO processes, showing that PECO process improves germination by 23.5% on the contaminated sample and 7.4% on the sample treated with PCO. These findings confirm that synergism of oxidation techniques could be a tractable way to resolve the problems related to recalcitrant compounds contained in wastewater.

Polyhydroxyalkanoates production from short and medium chain carboxylic acids by Paracoccus homiensis

The aim of this study was to evaluate an effect of short and medium chain carboxylic acids (CAs) rich stream derived from acidogenic mixed culture fermentation of acid whey on polyhydroxyalkanoates (PHAs) synthesis by Paracoccus homiensis and compare it with the impact of individual synthetic CAs. The obtained results confirmed that the analyzed bacterium is able to metabolize synthetic CAs as the only carbon sources in the growth medium with maximum PHAs production yields of 26% of cell dry mass (CDM). The replacement of the individual CAs by a CAs-rich residual stream was found to be beneficial for the Paracoccus homiensis growth. The highest biomass concentration reached about 2.5 g/L with PHAs content of 17% of CDM. The purified PHAs were identified as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by applying gas chromatography coupled with mass spectrometry, Fourier transform infrared spectroscopic spectra and UV–Vis spectra. Furthermore, a differential scanning calorimetric, thermogravimetric and water contact angle analysis proved that the extracted copolymers have useful properties. The obtained data are promising in the perspective of developing a microbial PHAs production as a part of an integrated valorization process of high CAs content waste-derived streams.