Successful Treatment of Invasive Fungal Infection Due to Highly Resistant Aspergillus calidoustus in an Allogeneic Hematopoietic Cell Transplant Recipient

Invasive aspergillosis (IA) is the most common invasive fungal infection following a hematopoietic cell transplant, with emerging cryptic species exhibiting resistance to commonly used antifungals such as azoles. These species have been increasingly found after the introduction of anti-mold prophylaxis. We report a case of a 56-year-old female with primary myelofibrosis whose allogeneic hematopoietic cell transplant was complicated by disseminated fungal infection (skin, lung) due to Aspergillus calidoustus, a cryptic specie. Treatment of Aspergillus species remains challenging as these cryptic species are usually resistant to azoles including voriconazole which is the first line of treatment of IA. Infection was successfully treated with surgical excision and combination antifungal therapy based on in vitro susceptibility and synergy testing. Therapy included isavuconazole, a drug that has been shown to be non-inferior to voriconazole in the treatment of invasive mold infections.

     

Kmasker plants – a tool for assessing complex sequence space in plant species

Many plant genomes display high levels of repetitive sequences. The assembly of these complex genomes using short high‐throughput sequence reads is still a challenging task. Underestimation or disregard of repeat complexity in these datasets can easily misguide downstream analysis. Detection of repetitive regions by k‐mer counting methods has proved to be reliable. Easy‐to‐use applications utilizing k‐mer counting are in high demand, especially in the domain of plants. We present Kmasker plants, a tool that uses k‐mer count information as an assistant throughout the analytical workflow of genome data that is provided as a command‐line and web‐based solution. Beside its core competence to screen and mask repetitive sequences, we have integrated features that enable comparative studies between different cultivars or closely related species and methods that estimate target specificity of guide RNAs for application of site‐directed mutagenesis using Cas9 endonuclease. In addition, we have set up a web service for Kmasker plants that maintains pre‐computed indices for 10 of the economically most important cultivated plants. Source code for Kmasker plants has been made publically available at https://github.com/tschmutzer/kmasker . The web service is accessible at https://kmasker.ipk-gatersleben.de .     

On the dynamic response of the anode in microbial fuel cells

A study of the dynamic response of a microbial fuel cell (MFC) using membrane electrode assemblies (MEAs) designed for air breathing cathode operation is reported. The MFC used four MEAs simultaneously and has a low internal resistance. An increased concentration of glucose produced a non-linear increase in the maximum current reached. The time to reach the maximum current increased with increasing glucose concentrations of 1-7 mM; varying from approximately 2.4 to 4.2h. The rate at which the current density increased with time was the same for all glucose concentrations up to current densities close to the maximum values. The peak power density varied approximately linearly with glucose concentrations from 2 to 77 mW/m(2) (1-7 mM) with a 1 kΩ resistance. The cell response appeared to be linked to a slow process of fuel transport to the bacteria and their metabolic processes. The dynamic response of the anode was analysed in terms of a substrate mass transport model. The application of different current ranges did not significantly change the dynamic response of either the anode community or the MFC polarization characteristics. Thus, it is likely that the bacterial communities that form under MFC operation contain sufficiently "dominant" electro-active species that are capable of producing high power for MFCs.     

Improved activity and stability of Rhizopus oryzae lipase via immobilization for citronellol ester synthesis in supercritical carbon dioxide

In present work, Rhizopus oryzae lipase immobilized on a film prepared using blend of hydroxylpropyl methyl cellulose (HPMC) and polyvinyl alcohol (PVA) was investigated for synthesis of citronellol esters with supercritical carbon dioxide (Sc-CO₂) as a reaction medium. The transesterification reaction was optimized for various reaction parameters like effect of molar ratio, acyl donor, time, temperature, enzyme concentration, effect of pressure and co-solvent to achieve the maximum yield of desired product. The results obtained signify remarkable increment (about eightfold) in the yield of citronellol acetate (91%) as compared to that of free lipase (11%) in Sc-CO₂. The developed biocatalytic methodology provides a substantial advantage of low biocatalyst loading (1.5%, w/v), lower reaction temperature (45 °C) and lower pressure (8 MPa) as compared to previous reports. The immobilization method has significantly enhanced the operational stability of lipase for ester synthesis under Sc-CO₂ conditions. The developed methodology was successfully applied for synthesis of three different industrially important citronellol esters namely citronellol acetate (91%), citronellol butyrate (98%), citronellol laurate (99%) with excellent yields using vinyl esters as acyl donor under Sc-CO₂ conditions. In addition, the immobilized biocatalyst was effectively recycled for three consecutive recycles.     

Evaluation of hydrolysis and fermentation rates in microbial fuel cells

This study determined the influence of substrate degradation on power generation in microbial fuel cells (MFCs) and microbial community selection on the anode. Air cathode MFCs were fed synthetic medium containing different substrates (acetate, glucose and starch) using primary clarifier sewage as source of electroactive bacteria. The complexity of the substrate affected the MFC performance both for power generation and COD removal. Power output decreased with an increase in substrate complexity from 99 ± 2 mW m⁻² for acetate to 4 ± 2 mW m⁻² for starch. The organic matter removal and coulombic efficiency (CE) of MFCs with acetate and glucose (82% of COD removal and 26% CE) were greater than MFCs using starch (60% of COD removal and 19% of CE). The combined hydrolysis–fermentation rate obtained (0.0024 h⁻¹) was considerably lower than the fermentation rate (0.018 h⁻¹), indicating that hydrolysis of complex compounds limits current output over fermentation. Statistical analysis of microbial community fingerprints, developed on the anode, showed that microbial communities were enriched according to the type of substrate used. Microbial communities producing high power outputs (fed acetate) clustered separately from bacterial communities producing low power outputs (fed complex compounds).     

Identification and characterization of 4-hexylbenzoic acid and 4-nonyloxybenzoic acid as substrates of CYP102A1

CYP102A1 is an efficient medium- to long-chain fatty acid hydroxylase that is able to accept a wide range of non-natural substrates which bear no resemblance to the natural ones. 4-Hexylbenzoic acid (HBA) and 4-nonyloxybenzoic acid (NOBA) were identified as CYP102A1 substrates via screening studies using the BD Oxygen Biosensor System. Spectroscopic binding studies showed that these two substrates bind in the active site of CYP102A1 with K _d values of 2.6 ± 0.1 μM for HBA and 1.9 ± 0.2 μM for NOBA. NADPH consumption rates in the presence of HBA and NOBA were 45 ± 1 min⁻¹ and 61 ± 1 min⁻¹, respectively. The coupling efficiency for NADPH was 57% for NOBA, while it was 77% for HBA. During whole-cell biotransformations, HBA was converted into ω−1- and ω−2-hydroxyhexylbenzoic acid, whereas NOBA was oxidized to ω−2-hydroxynonyloxybenzoic acid and ω−2,ω−4-dihydroxynonyloxybenzoic acid. HBA was used as a fatty acid mimic to compare whole-cell biotransformations with cell-free extracts. Whole-cell biotransformations carried out in a biphasic system resulted in 86% conversion of 5 mM HBA, producing 3.8 mM ω−2- and 0.5 mM ω−1-hydroxyhexylbenzoic acid in 4 h with a turnover number of 4.1 min⁻¹, whereas 100% conversion of 5 mM HBA was obtained in 1 h with crude cell extracts and a cofactor regeneration system, giving a turnover number of 10.5 min⁻¹.     

Glutamoyl diester of the dietary polyphenol curcumin offers improved protection against peroxynitrite-mediated nitrosative stress and damage of brain mitochondria in vitro: implications for Parkinson��s disease

Oxidative/nitrosative stress plays a crucial role in Parkinson's disease (PD) by triggering mitochondrial dysfunction. Nitrosative stress is mediated by reactive species such as peroxynitrite (PN) which could damage biomolecules thereby impinging on the cellular machinery. We observed that PN (0-1000 μM) inhibited brain mitochondrial complex I (CI) activity in a dose-dependent manner with concomitant tyrosine nitration of proteins. We also observed that exposure to PN at low concentrations (62.5-125 μM) significantly decreased the mitochondrial membrane potential and affected the mitochondrial integrity at higher doses (500-750 μM) as indicated by the mitochondrial swelling experiment. Therefore, it could be surmised that compounds that prevent such mitochondrial damage might have therapeutic value in neurological conditions such as PD. We previously showed that curcumin could detoxify PN and protect against CI inhibition and protein nitration. However, the therapeutic potential of curcumin is constrained by limited bioavailability. To address this issue and obtain improved antioxidants, three bioconjugates of curcumin (Di-demethylenated piperoyl, di-valinoyl and di-glutamoyl esters) were generated and tested against PN-mediated nitrosative stress and mitochondrial damage. We found that among the bioconjugates, the glutamoyl diester of curcumin showed improved protection against PN-dependent CI inhibition and protein nitration compared to other conjugates. Di-glutamoyl curcumin protected dopaminergic neurons against 1-methyl-4-phenylpyridinium (MPP(+))-mediated neuronal death. These effects were improved compared to curcumin alone suggesting that di-glutamoyl curcumin could be a better neuroprotective agent in neurodegenerative diseases such as PD.