Enzyme cascade converting cyclohexanol into ε-caprolactone coupled with NADPH recycling using surface displayed alcohol dehydrogenase and cyclohexanone monooxygenase on E. coli

The application of enzymes as biocatalysts in industrial processes has great potential due to their outstanding stereo‐, regio‐ and chemoselectivity. Using autodisplay, enzymes can be immobilized on the cell surface of Gram‐negative bacteria such as Escherichia coli. In the present study, the surface display of an alcohol dehydrogenase (ADH) and a cyclohexanone monooxygenase (CHMO) on E. coli was investigated. Displaying these enzymes on the surface of E. coli resulted in whole‐cell biocatalysts accessible for substrates without further purification. An apparent maximal reaction velocity V_MAX(app) for the oxidation of cyclohexanol with the ADH whole‐cell biocatalysts was determined as 59.9 mU ml⁻¹. For the oxidation of cyclohexanone with the CHMO whole‐cell biocatalysts a V_MAX(app) of 491 mU ml⁻¹ was obtained. A direct conversion of cyclohexanol to ε‐caprolactone, which is a known building block for the valuable biodegradable polymer polycaprolactone, was possible by combining the two whole‐cell biocatalysts. Gas chromatography was applied to quantify the yield of ε‐caprolactone. 1.12 mM ε‐caprolactone was produced using ADH and CHMO displaying whole‐cell biocatalysts in a ratio of 1:5 after 4 h in a cell suspension of OD_578nm 10. Furthermore, the reaction cascade as applied provided a self‐sufficient regeneration of NADPH for CHMO by the ADH whole‐cell biocatalyst.

Semi-quantitative analysis of cerebrospinal fluid chemistry and cellularity using urinary reagent strip: An aid to rapid diagnosis of meningitis

BACKGROUND

The examination of the cerebrospinal fluid (CSF) for proteins, glucose, and leukocytes still remains the basic gold standard investigation for the initial diagnosis of meningitis. Early diagnosis and initiation of antibiotics within 3 h can reduce the mortality and morbidity associated with meningitis. Hence, we conducted this study to document the usefulness of urinary reagent strip for the semi-quantitative analysis of CSF chemistry and cellularity.

MATERIALS AND METHODS

All clear CSF samples were subjected for two types of tests, the definitive test and the index test. CSF microscopy and biochemical values are considered as definitive. Combur-10 urinary reagent strip was used as the index test for proteins, glucose, and leukocytes. The diagnostic accuracy of each index test was calculated using different cut-off levels (leukocyte esterase positivity 1+ vs. CSF granulocytes ≥10/cumm, proteins 1+ and 2+ vs. CSF protein ≥30 mg/dl and ≥100 mg/dl, respectively, and glucose 0 vs. ≤40 mg/dl and ≤50 mg/dl). Statistical analysis was performed to derive the specificity, sensitivity, positive predictive value, negative predictive value, likelihood ratio (LR)+, LR-, and area under curve (AUC).

RESULTS

The study subjects comprised 103 cases. The strip showed a high sensitivity and specificity for leukocytes ≥10 cells/cumm. The strip showed a sensitivity of 96% and a specificity of 87.1% for proteins at a cut-off ≥100 mg/dl while the strip was less specific at a cut-off of ≥30 mg/dl. With respect to glucose, the strip was highly specific (100%) and less sensitive at both the cut-off levels. The AUC for leukocytes ≥10 cells/cumm was 99.05%; for proteins ≥30 mg/dl and ≥100 mg/dl, it was 84.86% and 95.69%, respectively; and, for glucose ≤40 mg/dl and ≤50 mg/dl, it was 86.51% and 76.99%, respectively.

CONCLUSION

The routinely used urinary reagent strip can be utilized for the rapid analysis of CSF. If implemented, this technique will be useful in rural areas. It would also decrease the turnaround time in centers where the facility is available.

Co-expression of an alcohol dehydrogenase and a cyclohexanone monooxygenase for cascade reactions facilitates the regeneration of the NADPH cofactor

The introduction of a three-enzyme cascade (comprising a cyclohexanone monooxygenase (CHMO), an alcohol dehydrogenase (ADH) and a lipase (CAL-A)) for the production of oligo-ε-caprolactone provided self-sufficiency with respect to NADPH-cofactor regeneration and reduced inhibiting effects on the central CHMO enzyme. For further optimization of cofactor regeneration, now a co-expression of CHMO and ADH in E. coli using a Duet™ vector was performed. This led to higher conversion values of the substrate cyclohexanol in whole-cell biocatalysis compared to an expression of both enzymes from two separate plasmids. Furthermore, a more advantageous balance of expression levels between the partial cascade enzymes was achieved via engineering of the ribosome binding site. This contributed to an even faster cofactor regeneration rate.

Iniencephaly: Radiological and pathological features of a series of three cases

Iniencephaly is a rare form of neural tube defect with an incidence of 0.1-10 in 10,000 pregnancies. It is characterized by the presence of occipital bone defects at foramen magnum, fixed retroflexion of head, spinal dysmorphism, and lordosis of cervicothoracic vertebrae. It is usually associated with central nervous system, gastrointestinal, and cardiovascular anomalies. We present radiological and autopsy findings in a series of 3 cases of iniencephaly (gestational ages 29.3, 23, and 24 weeks) first fetus in addition showed omphalocele, pulmonary hypoplasia, two lobes in right lung, accessory spleen, atrial septal defect, bilateral clubfoot, ambiguous genitalia, and single umbilical artery. Second fetus was a classical case of iniencephaly apertus with spina bifida. Third fetus had colpocephaly and bifid spine.

Pigmented Paget's disease of nipple: A diagnostic challenge on cytology

Paget's disease is a rare form of breast cancer often associated with an underlying ductal carcinoma in situ or invasive cancer. A 47-year-old female patient presented with bleeding from the left nipple since 4 months. Imprint smears from the lesion showed pleomorphic malignant epithelial cells in singles and in small clusters, many of them containing dark brown cytoplasmic pigment granules. There was no palpable breast lump or axillary lymph node enlargement. Based on the physical examination and cytological features, a diagnosis of malignant melanoma with a differential of Paget's disease of the nipple was made. Biopsy showed features of Paget's disease and immunohistochemistry was positive for HER-2/neu, negative for HMB-45 and S-100, thus confirming the diagnosis. This case has been reported to emphasize the fact that Paget's cells can contain imbibed brown cytoplasmic pigment and should not be mistaken for melanoma cells on cytology smears.

Solitary intramammary schwannoma mimicking phylloides tumor: Cytological clues in the diagnosis

A 30-year-old woman presented with a huge exophytic lobulated mass in the right breast, clinically and radiologically resembling phylloides tumor. Fine needle aspiration cytology smears showed clusters and singly scattered spindle cells along with structures reminiscent of verocay bodies. However, the epithelial elements were absent. A cytological diagnosis of benign mesenchymal spindle cell lesion, suggestive of schwannoma was rendered. Subsequent histopathological examination and strong S-100 positivity of tumor cells on immunohistochemistry confirmed the diagnosis.Breast is an uncommon location for benign schwannoma. The present case describes the unusual clinical picture, highlights cytological features and discusses the differential diagnoses of schwannoma from other benign spindle cells lesions of the breast on cytology smears.