Time-of-flight Mass Spectrometry Research Articles

Proteome analysis of propolis deciphering the origin and function of its proteins

Propolis is a resinous honeybee product, rich in polyphenolic compounds and with high economic value. Although extensive studies regarding the chemical composition of different propolis extracts have been carried out, the propolis proteome remained unknown. The present study aimed at characterizing the proteome of two geographically-distinct propolis originating from Belgium and Iran. Propolis extracts were analyzed by sodium dodecyl sulfate polyacrylamide gel (SDS-PAGE) followed by Matrix Assisted Laser Desorption Ionization – Time of Flight Mass Spectrometry (MALDI-TOF MS) and Liquid chromatography-electrospray ionization MS (LC-ESI-MS) analyses. Our comprehensive proteomic analysis led to the identification of honeybee venom and royal jelly proteins, and numerous plant-defense proteins in propolis, extending our understanding of the antimicrobial properties of this complex natural substance. The proteome of both propolis was mainly made up of proteins belonging to the poplar tree. Pathogenesis-related (PR) proteins, poplar PR-2 (β-1,3-glucanases) and PR-8 (acidic endochitinases) were found to be the major components of both propolis extracts, while the major bee venom allergen (Api m 1) and royal jelly proteins (MJRP 1, 2, 3 and 5) were identified in the propolis from Belgium. Overall, our proteome analyses revealed that propolis extracts from Belgium and Iran shared a core protein composition originating from the poplar proteome. The majority of identified proteins are involved in the plant defense against pathogens, most belonging to well-known pathogenesis-related families. Proteomics could thus represent a viable approach for origin authentication and allergen identification in poplar-type propolis.

Solute Enrichment in the Fusion Zone during Resistance Spot Welding of a Third Generation Advanced High Strength Steel

Resistance spot welding is a critical joining technique in automobile assembly. The load carrying properties of spot welds are generally accepted to correlate with weld diameter, which increases with increasing weld current or duration. The formation of a softened layer, or weld halo, surrounding the fusion zone in a spot-welded third generation (Gen3) advanced high strength steel (AHSS) was recently reported in the literature. To optimize weld performance by schedule design, it is necessary to understand the halo formation characteristics and potential impacts. Accordingly, welding of a Gen3 AHSS was performed using weld times between 130 – 1300 ms. Microhardness mapping characterized weld microhardness and the evolution of the halo during welding. Electron probe microanalysis and timeof-flight secondary ion mass spectrometry enabled measurement of solute distributions through the weld halo, while scanning electron microscopy was used for microstructural characterization. The solidified structure was examined using light-optical microscopy, and with the microhardness and compositional data, used to infer the mechanism by which the halo forms during welding. It was found that the halo develops due to solute rejection from a cellular solidification front that advances towards the center of the fusion zone while weld current is applied. Extended weld times increase the size of the weld halo and the solute content of the inner fusion zone. The decrease in weld halo microhardness and the increase in inner fusion zone microhardness is largely explained by the changes in local carbon content associated with halo formation.

614. Experience with Using MALDI-TOF MS to Diagnose Clinically Significant Filamentous Fungal Isolates

Abstract Background Matrix assisted laser desorption/ionisation time of flight mass spectrometry (MALDI-TOF MS) technology has revolutionised bacterial diagnostics. Filamentous fungi are a varied and important group of pathogens that cause a wide spectrum of clinical disease. Identification of these traditionally relies upon highly experienced practitioners identifying unique fungal morphological characteristics, along with specific molecular techniques, but MALDI-TOF MS may be a useful alternative. The aim of this retrospective review was to determine how useful MALDI-TOF MS was as an adjunct to filamentous fungi identification at our laboratory service. Methods All fungal diagnoses made at St Vincent’s Pathology Melbourne, a large metropolitan laboratory servicing multiple tertiary hospitals and community pathology centres, from 2018 to 2022 were extracted. For clinically significant filamentous fungal isolates, the method of diagnosis was reviewed and categorised into; morphological diagnosis, Bruker MALDI Biotyper® diagnosis, and national reference laboratory diagnosis. All clinically significant isolates where MALDI-TOF MS was attempted were also reviewed. Results A total of 256 clinically significant isolates were extracted and reviewed. MALDI-TOF MS was attempted in 59 of these, with success in 39 (66.1%). Of the 20 cases where MALDI-TOF MS was attempted but did not identify the isolate, 16 were diagnosed morphologically and four required send out to the national reference laboratory. 71.2% of MALDI-TOF MS attempts were in the 2021-22 period when successful identification occurred 80.9% of the time. No species/genus appeared more or less readily identifiable. Of the remaining cases, 208 were identified morphologically and nine using the national reference laboratory. Conclusion MALDI-TOF MS performed modestly well at identifying filamentous fungi during this study period. Increased use and successful isolate identification in the 2021-22 period likely reflects improvement in the Bruker MALDI-TOF MS database for filamentous fungi. The MALDI-TOF MS system is a useful option in the identification of clinically significant filamentous fungi however morphological and molecular techniques remain important. Disclosures All Authors: No reported disclosures

868. Early Organism Identification by Matrix Assisted Laser Desorption Ionization Time Of Flight Mass Spectrometry (MALDI TOF MS) Decreases the Time to Optimal Antibiotic Therapy for Common Bacterial Infections

Abstract Background MALDI-TOF helps in precise identification of microorganisms from positive cultures. It is based on the principle of proteomics and obviates the need for the use of biochemicals. It reduces the turnaround time for reporting microbiologic cultures. Early identification and reporting of the organism, before the availability of antimicrobial susceptibilities, may reduce the time to first antibiotic modification and impact the clinical outcomes of patients. Methods This is a prospective observational two-arm comparative study conducted at a tertiary care centre in North India, with a sample size of 50 patients in the conventional arm and 100 patients in the interventional arm. The workflow of both arms are depicted in figure 1&2. The study population included patients in the medical ward and intensive care units (ICU) with positive cultures. The primary objective of this study was to compare the average time to first antibiotic modification post-culture positivity in the conventional and interventional arms and to compare clinical outcomes of patients in both arms. Escalation, de-escalation and any modification in antibiotics were also recorded. Results The median time to first antibiotic modification was significantly shorter in the intervention arm compared to the conventional arm (2010 mins vs 2905 mins, p=0.002). Overall 44/100 antibiotic modifications were made in the interventional arm out of which 43.2% (19/44) were made based on the MALDI report alone without awaiting susceptibilities. The major type of modification was the de-escalation of antibiotics (47.4%). Mortality rates were 32% in the conventional arm and 27% in the intervention arm, but the difference was not statistically significant (p=0.52) (table 1). Conclusion MALDI-TOF helps in the early modification of antibiotics. The major utility is in the de-escalation of unnecessary antibiotics. Coupled with a robust antimicrobial stewardship programme, this modality can help in reducing antibiotic use. Disclosures All Authors: No reported disclosures

728. Potential Reservoirs for Additional Carbapenemase Gene Spread: Detection of Carbapenemase Genes in non-Pseudomonas aeruginosa and non-Acinetobacter baumannii isolates

Abstract Background Public Health Laboratories (PHL) across 50 U.S. states, several cities and Puerto Rico participate in CDC’s Antimicrobial Resistance Laboratory Network (AR Lab Network), to test clinical isolates of carbapenem-resistant Pseudomonas aeruginosa (CRPA) and Acinetobacter baumannii (CRAB) for the presence of targeted carbapenemase (CP) genes. PHLs have submitted reports of these targeted genes in CR non-aeruginosa Pseudomonas (CR-NAP) and non-baumannii Acinetobacter (CR-NBA) isolates. Here we describe the ad-hoc detection of targeted CP genes in CR-NAP and CR-NBA species tested by the Network. Methods Clinical laboratories submitted CR isolates to PHLs for organism identification. Isolates were deemed suspected CR-NAP and CR-NAB when a PHL ruled out aeruginosa or baumannii, respectively, but their MALDI ToF MS database prevented further speciation. PHLs used real-time polymerase chain reaction or whole genome sequencing to detect the presence of targeted CP genes: blaKPC,blaNDM,blaOXA-48-like,blaIMP, and blaVIM in Pseudomonas and Acinetobacter, and blaOXA-23-like,blaOXA-24/40-like, and blaOXA-58-like in Acinetobacter. Results During 2017–2021, the AR Lab Network tested 56,092 CR-Pseudomonas isolates, 71 of which were CR-NAP; P. putida (n=15; 21%), P. fluorescens (12; 17%) P. otitidis (5; 7%), P. monteilii (3; 4%), 1 (1%) each of P. koreensis and P. mosselii, and 34 (48%) other suspected CR-NAP. Three (4%) of the 71 CR-NAP isolates tested carried a targeted CP gene: 1 P. fluorescens with blaIMP, 1 P. putida with blaVIM, and 1 P. Japonica with blaKPC. Of 13,624 CR-Acinetobacter isolates tested, 25 (< 1%) were CR-NBA; A. pitti (10; 40%), A. radioresistens (6; 24%), A. variabilis (2; 8%), 1 (4%) each of A. berezinaiae, A. lwoffii, and A. ursingii, and 4 (16%) other suspected CR-NBA. The A. variabilis isolates each harbored both blaNDM and blaOXA-58-like genes. Conclusion Although CR-NAP and CR-NBA isolates are not solicited by the Network, some of these species are submitted for characterization. Our findings suggest these other species do harbor some targeted CP genes and may represent unmonitored reservoirs for CP gene spread in the U.S. An expansion of testing to include these species in the AR Lab Network may improve our ability to slow the spread of antimicrobial resistance. Disclosures All Authors: No reported disclosures

Production and characterization of a biosurfactant produced by Bacillus amyloliquefaciens C11 for enhancing the solubility of pesticides

The production and characterization of lipopeptide biosurfactant obtained from a novel bacterial strain Bacillus amyloliquefaciens C11 isolated from a biopurification system, to enhance the solubility of three pesticides of environmental concern was investigated. Biosurfactant production by B. amyloliquefaciens C11 was evaluated in a 2-L reactor and characterized by chromatographic and spectroscopic methods. Biosurfactant production was associated with bacterial growth and glucose consumption. The produced biosurfactant decreased the surface tension of water from 72 to 28 mN m−1 at 24 h of incubation, with critical micelle concentration (CMC) of 51.5 mg L−1. The polymerase chain reaction for determining the presence of srfAA gene in B. amyloliquefaciens C11 was carried out. The strain exhibited the presence of srfAA gene with amplification at 201 bp, which is specific to surfactin homologues. The production of surfactin was corroborated by high performance liquid chromatography (HPLC) and matrix-assisted laser desorption/ionization time-of flight mass spectrometry (MALDI-TOF-MS) analyses. The HPLC analysis showed six isoforms of surfactin, being the isoform D found in mayor percentage (41%). Thermal gravimetric analysis (TGA) revealed the thermostability of the biosurfactant. The obtained biosurfactant maintained its properties during exposure to temperatures in range of 30–80 °C and pH values in range of 5–9. The surfactin produced by B. amyloliquefaciens C11 increased the solubility in water of chlorpyrifos, iprodione and atrazine by 7.5-fold, 1.3-fold, and 1.4-fold, respectively. Our results show that the biosurfactant produced by B. amyloliquefaciens C11 improves the bioavailability of pesticides and consequently could improves the efficiency of bioremediation processes.

Comparison of the Bruker Microflex LT and Zybio EXS2600 MALDI TOF MS systems for the identification of clinical microorganisms

The emergence of Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI TOF MS) technology has expanded the capabilities for identifying microorganisms in clinical labs, replacing traditional biochemical testing with a proteomic approach. In the present study, we compared results between the two commercial MALDI TOF MS systems, Bruker Microflex LT Biotyper and Zybio EXS2600 Ex-Accuspec, for the identification of 1979 urinary isolates by direct extraction method. Current study found that both systems identified a high percentage of isolates to at least the genus level – Bruker 95.6 % of isolates, Zybio 92.4 %. In the case of 89.5 % of all analyzed spectra, the identification results were consistent between the used devices. The highest score values and the highest percentage of spectra identified to species were obtained for gram-negative bacteria. The results show that both systems are equally good choices in terms of analytical performance for routine microbiological diagnostic procedures.

Characterization of key aroma compounds in Rice flavor baijiu from different rice raw materials by gas chromatography-ion mobility spectrometry and gas chromatography-olfactometry-quadrupole time of flight mass spectrometry

Rice flavor baijiu is one of the four traditional Chinese liquors, but the flavor difference caused by rice raw materials has received little attention. In this study, gas chromatography-ion mobility spectrometry (GC-IMS) combined with gas chromatography-olfactometry-quadrupole time of flight mass spectrometry (GC-O-QTOF/MS) were used to analyze five Rice flavor baijiu brewed from different rice raw materials. The results showed that there was a significant difference in the number and content of aroma compounds between the baijiu made from japonica rice and indica rice, and a total of 34 volatiles were characterized by the GC-IMS technique, which effectively constructed the fingerprint profile of the flavor differences of Rice flavor baijiu. GC-O-QTOF combined with aromatic extract dilution analysis (AEDA) tests identified 42 characteristic aroma active regions, 34 of which could be identified and quantified by the internal standard method. Sixteen aroma-active compounds in five baijiu samples showed high odor activity values (OAV). In addition, multivariate statistical analyses such as principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) effectively revealed the distribution patterns of the samples and their separation of relevant aroma activity markers. Six key aroma compounds, including isopentyl acetate, ethyl hexanoate, benzeneacetaldehyde, phenethyl acetate, undecane-2-one, and ethyl decanoate, were screened to have a greater effect on the flavor of Rice flavor baijiu.

Detection of tuberculosis-associated compounds from human skin by GCxGC-TOFMS

Tuberculosis (TB) remains a global health concern. This study aimed to investigate the potential of human skin volatile organic compounds (VOCs) as prospective biomarkers for TB diagnosis. It employed a non-invasive approach using a wearable silicone rubber band for VOC sampling, comprehensive gas chromatography – time of flight mass spectrometry (GCxGC-TOFMS), and chemometric techniques. Both targeted and untargeted biochemical screening was utilized to explore biochemical differences between healthy individuals and those with TB infection. Results confirmed a correlation between compounds found in this study, and those reported for TB from other biofluids. In a comparison to known TB-associated compounds from other biofluids our analysis established the presence of 27 of these compounds emanating from human skin. Additionally, 16 previously unreported compounds were found as potential biomarkers. The diagnostic ability of the VOCs selected by statistical methods was investigated using predictive modelling techniques. Artificial neural network multi-layered perceptron (ANN) yielded two compounds, 1H-indene, 2,3 dihydro-1,1,3-trimethyl-3-phenyl; and heptane-3-ethyl-2-methyl, as the most discriminatory, and could differentiate between TB-positive (n = 15) and TB-negative (n = 23) individuals with an area under the receiver operating characteristic curve (AUROC) of 92 %, a sensitivity of 100 % and a specificity of 94 % for six targeted features. For untargeted analysis, ANN assigned 3-methylhexane as the most discriminatory between TB-positive and TB- negative individuals. An AUROC of 98.5 %, a sensitivity of 83 %, and a specificity of 88 % were obtained for 16 untargeted features as chosen by high performance variable selection. The obtained values compare highly favourable to alternative diagnostic methods such as breath analysis and GeneXpert. Consequently, human skin VOCs hold considerable potential as a TB diagnostic screening test.

Nanomolar level colorimetric and On–Off fluorimetric sensing of Cu2+: Theoretical, Smartphone, test kit and food application outcomes

A novel naphthaldehyde–based colorimetric and fluorogenic molecular sensor PHNAP [(E)–1–(((4–(phenylamino)phenyl)imino)methyl)naphthalen–2–ol] was developed for the recognition of Cu2+ with outstanding selectivity. After treatment with Cu2+, the PHNAP showed remarkable color transforms from ''yellow'' to ''colorless'' under UV–cabin and ''yellow'' to ''pink'' under daylight. Under the optimum sensing conditions, Cu2+ was selectively recognized and sensitively determined with a nanomolar detection limit (6.61 nM; 3σ/K). The PHNAP showed very fast and Cys-reversible response for Cu2+. The Job's plot and TOF–MS data were gathered to authenticate the mechanism of the binding. The DFT calculations also confirmed the proposed sensing phenomenon. Furthermore, PHNAP–based portable test kits were simply fabricated for the visual recognition of Cu2+. The PHNAP was used in diverse samples for the quantitatively recognition of Cu2+; likewise, the smartphone appliance was successfully performed without the aid of any sophisticated tool and the outstanding visual response of PHNAP.

Characterization of polymerized impurities in cefoxitin sodium for injection by two-dimensional chromatography coupled with time-of-flight mass spectrometry

Polymerized impurities in β-lactam antibiotics can induce allergic reactions, which seriously threaten the health of patients. In order to study the polymerized impurities in cefoxitin sodium for injection, a novel approach based on the use of two-dimensional liquid chromatography coupled with time-of-flight mass spectrometry (2D-LC-TOF MS) was applied. In the 1st dimension, high performance size exclusion chromatography (HPSEC) with a TSK-G2000SWxl column was employed. Column switching was applied for the desalination of the mobile phase used to separate polymerized impurities in the 1st dimension before they were transferred to the 2nd dimension which utilized reversed phase liquid chromatography (RP-LC) and TOF MS for further structural characterization. The structures of four polymerized impurities (which were all previously unknown) in cefoxitin sodium for injection were deduced based on the MS2 data. One novel polymerized impurity (PI–I), with 2H less than the molecular weight of two molecules of cefoxitin (Mr. 852.09), was found to be the most abundant (>50 %) in almost all the samples examined and could be regarded as the marker polymer of cefoxitin sodium for injection. This work also showed the great potential of the 2D-LC-TOF MS approach in structural characterization of unknown impurities separated with a mobile phase containing non-volatile phosphate in the 1st dimension.

Exposure and human health risk assessment of chlorinated paraffins in indoor and outdoor dust from a metropolitan city, Lahore, Pakistan

Chlorinated paraffins (CPs) are widely used in commercial products due to their stability and durability and are subsequently released in the environment posing serious health risks in human population. In this study, dust samples from indoor and outdoor settings of residential, commercial and industrial zones as well as from vehicles were collected from a metropolitan city, Lahore, Pakistan. A total of 83 dust samples were analyzed for short (SCCPs) and medium (MCCPs) chained CPs through quadrupole time of flight mass spectrometer in atmospheric pressure chemical ionization (APCI QToF-MS) mode. The median concentrations of ƩCPs (C10-17) in outdoor dust were higher than indoor dust in industries (0.97 vs 0.48 μg/g), and residential areas (0.70 vs 0.13 μg/g) while lower in commercial areas (0.28 vs 0.44 μg/g) reflecting their higher prevalence in industrial and residential zones. The vehicular dust had median ƩCPs of 0.16 μg/g which was similar to residential indoor dust. Overall, ƩSCCPs were dominant among all zones with C10,12 and Cl7-8 as abundant carbon and chlorine congeners in both indoor and outdoor dusts. No significant correlations were observed between indoor and outdoor dust for ƩSCCPs and ƩMCCPs indicating their varying exposure. Health hazard index and margin of exposure revealed that toddlers were at higher risk compared to adults as a results of CPs exposure from both indoor and outdoor environments. This is the first ever assessment of CPs in Pakistan reflecting higher prevalence of SCCPs than MCCPs in dust of local environment posing some serious health consequences hence needed intensive investigation and effective management.

Lipidomics Reveals the Effects of Detergents on Skin Surface Lipids in Young Adults

Background: Detergent is a chemical product commonly used in people’s daily life. Contact with detergent solutions can damage the human skin barrier and cause skin diseases. Skin surface lipids (SSLs) play a decisive role in skin barrier function. This study aimed to observe the changes of SSLs in young adults after exposure to detergent solutions to explore the underlying mechanism of skin barrier function damage. Methods: A self-controlled study on youth adults was conducted in Zhengzhou, China, in November 2020. The study lasted for a total of 1 week, and skin barrier function was assessed by trans-epidermal water loss (TEWL) values. The changes of SSLs before and after exposure to the detergent with subjects were measured using ultra-performance liquid chromatography quadrupole time of flight mass spectrometry. Results: The skin barrier function of subjects’ hands was impaired after exposure to detergent (TEWL value increased, p < 0.001). A total of 520 SSLs were detected, divided into 6 main categories. The average relative abundance of these 6 major lipids decreased after exposure. Sphingolipids (mainly ceramides), free fatty acids (mainly long-chain fatty acids), cholesterol lipids, and glycerophospholipids are the most severely damaged lipids. Conclusion: Detergent solutions can damage the skin barrier function and SSLs of young hands; interventions targeting SSLs to eliminate detergent damage to human skin may be of value.

Occurrence and Antimicrobial Resistance among Staphylococci Isolated from the Skin Microbiota of Healthy Goats and Sheep.

Staphylococci colonize the skin and mucous membranes of different animals. The purpose of this study was to determine the staphylococcal composition of the skin microbiota of healthy, non-vet visiting, and antimicrobially non-treated sheep and goats. In total, 83 strains (44 from goats and 39 from sheep) were isolated and identified using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). The diversity of the isolated Staphylococcus species was relatively high, and only coagulase-negative staphylococci (CoNS) were isolated. In sheep, S. vitulinus (9/39, 23.1%) was the most common species, followed by S. equorum (8/39, 20.5%), S. lentus (7/39, 17.9%), S. sciuri (6/39, 15.4%), S. xylosus (6/39, 15.4%), S. warneri (1/39, 2.6%), S. simulans (1/39, 2.6%), and S. nepalensis (1/39, 2.6%). In the goats, the most common species was S. sciuri, which was detected in 13 (29.5%) animals. The goat skin was also inhabited by S. equorum (7/44, 15.9%), S. vitulinus (6/44, 13.6%), S. cohnii (5/44, 11.4%), S. lentus (4/44, 9.1%), S. suscinus (3/44, 6.8%), S. caprae, (2/44, 4.5%), S. auricularis (2/44, 4.5%), S. warneri (1/44, 2.3%), and S. xylosus (1/44, 2.3%). Only one S. xylosus strain of goat origin carried the enterotoxin gene (sea). Antimicrobial resistance was not common among the isolated staphylococci. Only 31 (37.3%) strains were resistant to at least one antimicrobial agent, with the highest frequency of resistance to penicillin (16.8%), followed by clindamycin (9.6%), erythromycin (8.4%), moxifloxacin (8.4%), and tetracycline (7.2%). All isolates were susceptible to eight antibiotics (amikacin, gentamycin, ciprofloxacin, levofloxacin, rifampicin, chloramphenicol, trimethoprim-sulfamethoxazole, and tigecycline), representing six different classes. Three isolates displayed a multi-resistance phenotype (MDR): the goat isolates S. cohnii and S. sciuri, as well as the ewe isolate S. xylosus. The MDR S. cohnii isolate was found to be methicillin-resistant and carried the mecA gene. Moreover, the staphylococci isolated from the healthy animals carried genes conferring resistance to β-lactams (mecA, blaZ), tetracyclines (tetL, tetK), macrolides (ermB, ermC), lincosamides (lnu), and fluoroquinolones (grlA). However, the prevalence of these genes was low.

Rapid AMR prediction in Pseudomonas aeruginosa combining MALDI–TOF MS with DNN model

Abstract Background Pseudomonas aeruginosa is a significant clinical pathogen that poses a substantial threat due to its extensive drug resistance. The rapid and precise identification of this resistance is crucial for effective clinical treatment. Although matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF MS) has been used for antibiotic susceptibility differentiation of some bacteria in recent years, the genetic diversity of P. aeruginosa complicates population analysis. Rapid identification of antimicrobial resistance (AMR) in P. aeruginosa based on a large amount of MALDI–TOF-MS data has not yet been reported. In this study, we employed publicly available datasets for P. aeruginosa, which contain data on bacterial resistance and MALDI–TOF-MS spectra. We introduced a deep neural network model, synergized with a strategic sampling approach (SMOTEENN) to construct a predictive framework for AMR of three widely used antibiotics. Results The framework achieved area under the curve values of 90%, 85%, and 77% for Tobramycin, Cefepime, and Meropenem, respectively, surpassing conventional classifiers. Notably, random forest algorithm was used to assess the significance of features and post-hoc analysis was conducted on the top 10 features using Cohen’s d. This analysis revealed moderate effect sizes (d = 0.5–0.8) in Tobramycin and Cefepime models. Finally, putative AMR biomarkers were identified in this study. Conclusions This work presented an AMR prediction tool specifically designed for P. aeruginosa, which offers a hopeful pathway for clinical decision-making.

Isolation, screening, and identification of chitinase-producing bacterial strains from riverbank soils at Ambo, Western Ethiopia

Chitinases are hydrolytic enzymes that dissolve the glycosidic linkages in chitin. Chitin is a cell wall component of fungi and fund in exoskeleten of worms and arthropods. Chitinase has been applied in agriculture, as a biopesticide for the control of plant fungal infections, in medicine, and in waste management. This research aimed to isolate, screen, and identification of chitinase-producing bacteria from riverbank soils. Twenty nine chitinolytic bacteria were isolated from the river bank soil samples, from which 9 of them had strong chitinolytic properties. Chitinase production was determined by zones of hydrolysis produced after 96 h of incubation at 37 °C. The different bacterial isolates were characterized morphologically, microscopically, and biochemically and finally eight strain were identified at species level by Matrix Assisted Laser Desorption Ionization - Time of Flight Mass Spectrometry (MALDI–TOF MS). From the eight, bacterial isolates investigated in this study Stenotrophomonas maltophilia showed the highest chitinase enzyme activity (625 μg/mL) followed by Pseudomonas putida with the enzyme activity of (553 μg/mL) and the least enzyme activity was recorded for Lilliottia amnigena (80 μg/mL). An incubation temperature of 45 °C, neutral pH and an incubation period of 96 h are found to be the optimum condition for the chitinase enzyme production from Stenotrophomonas maltophilia. The results of this study indicated the possibility of the production of chitinase from the chitinolytic bacterial isolates, which was highly useful for a variety of applications, including biocontrol of harmful insects and pathogenic fungi as well as in the biochemical, pharmaceutical, and medical sectors.

Proterozoic to Phanerozoic case studies of laser ablation microanalysis for microbial carbonate U–Pb geochronology

Some of the earliest bio-sedimentary records of life on Earth are represented by microbial carbonates, which are also critical geochemical archives of ancient seawater chemistry and the environmental circumstances in which they precipitated. Reconstructing paleo-microbial environments on Earth and potentially other planets requires precise determination of the depositional ages of these materials. The (abiogenic) carbonate geochemistry communities can now use developments in in-situ laser ablation U-Pb dating using inductively coupled plasma mass spectrometry (LA-ICP-MS). Due to the effects of impurity mixing and diagenesis, microbial carbonates have received little geochronological study despite their broad relevance for understanding ancient seawater's environmental conditions and geochemical compositions. This study demonstrates using time-of-flight mass spectrometry (TOF-MS) to perform quick, quantitative elemental mapping before U-Pb spot dating to improve experiment success rates and data reliability and offers four practical application examples.

Optimizing the identification of thiols in red wines using new oak-wood accelerated reductive treatment

This study proposes a new method for identifying thiols in red wines by mimicking specific chemical mechanisms that occur during bottle-aging. It involves the reaction of oak-wood extracts with hydrogen sulfide and the reduction of disulfides with DIBAL. After optimization of the reaction conditions, the aroma of fresh oak wood turned into intense “meaty” nuances reminiscent of the aging bouquet of red wines. Samples were analyzed by gas chromatography coupled with olfactometry (GC-O) and coupled with a pulsed flame photometric detector. This resulted in the identification of six odorant zones with meaty descriptors associated with sulfur compounds. One of the odorant zones was identified as 2-methoxybenzenethiol by using heart-cutting multidimensional GC coupled with olfactometry and time of flight mass spectrometer. Its identification in aged red wines was confirmed by GC coupled with tandem mass spectrometry analyses. Five other thiols associated with oak-wood precursors were also identified in red wines.

Chemical constituents from Mytilaria laosensis Lec. leaves and branches

Phytochemical investigations on the leaves and branches of Mytilaria laosensis Lec. led to the isolation of eight compounds, including four ecdysteroids (1-4), three flavonoids (5–7), and one phenylpropanoid (8). The identification of isolated compounds was achieved on the basis of NMR data, mass spectral data, and comparison with previous literature data. These eight compounds were isolated from M. laosensis for the first time. In addition, compounds 1–4 and 8 were found for the first time in the Hamamelidaceae family. Furthermore, the metabolite profiling of ethyl acetate and n-butanol fractions of M. laosensis were also measured by using liquid chromatography coupled with ion trap and time of flight mass spectrometry (LCMS-IT-TOF). The results of LCMS-IT-TOF analysis showed that this plant has other ecdysteroids and glycosides besides the eight isolated constituents. The chemotaxonomic significance of these compounds was discussed.

Chemical elucidation of recycled plastic pyrolysis oils by means of GC×GC-PI-TOF-MS and GC-VUV

Detailed chemical characterization of the composition of pyrolysis oils produced from plastics is a mandatory step in understanding the recycling process. Even though the chemical composition of pyrolysis plastic waste oils shows similarities with fossil-based oils, e.g. PIONA related compounds, the relative proportions of the chemical classes are significantly different, resulting in important changes in the global properties of these fluids. In this context, an analytical method based on comprehensive two-dimensional gas chromatography (GC×GC), coupled with photoionization (PI) – time-of-flight mass spectrometry (TOF MS) was developed to obtain a detailed chemical characterization of plastic pyrolysis-oil. A group-type analysis was achieved thanks to the detection of molecular ions by soft ionization PI-TOF MS. Moreover, olefins were successfully distinguished from naphthenes by in-depth consideration of MS spectra, even though such compounds elute very close in the 2D chromatographic separation space. A part of the olefins identified by PI was further confirmed by GC coupled to vacuum ultraviolet detection (VUV) since olefins VUV spectra differ from other compounds. The overall combination of the entire set of data of this multi-modal approach was valuable in studying the pyrolyzed plastic oil composition. It was furthermore applied to monitor the efficiency of upgrading processes that were applied to the oils to remove specific contaminants such as the diolefins. This approach has the potential to support the production of plastic pyrolysis oils that could efficiently be reintroduced in the market to sustain economic circularity needs.