Challenges and Advances in the Bioproduction of L-Cysteine

L-cysteine is a proteogenic amino acid with many applications in the pharmaceutical, food, animal feed, and cosmetic industries. Due to safety and environmental issues in extracting L-cysteine from animal hair and feathers, the fermentative production of L-cysteine offers an attractive alternative using renewable feedstocks. Strategies to improve microbial production hosts like Pantoea ananatis, Corynebacterium glutamicum, Pseudomonas sp., and Escherichia coli are summarized. Concerning the metabolic engineering strategies, the overexpression of feedback inhibition-insensitive L-serine O-acetyltransferase and weakening the degradation of L-cysteine through the removal of L-cysteine desulfhydrases are crucial adjustments. The overexpression of L-cysteine exporters is vital to overcome the toxicity caused by intracellular accumulating L-cysteine. In addition, we compiled the process engineering aspects for the bioproduction of L-cysteine. Utilizing the energy-efficient sulfur assimilation pathway via thiosulfate, fermenting cheap carbon sources, designing scalable, fed-batch processes with individual feedings of carbon and sulfur sources, and implementing efficient purification techniques are essential for the fermentative production of L-cysteine on an industrial scale.

Assessment of sensitivity to the anesthesia in a diabetic rat model

OBJECTIVE

Diabetes mellitus and glucose regulation are important in deciding on surgical intervention in pre-surgical assessments. In our study, we aimed to investigate the correlations between the induction time of anesthesia, glucose level, and weight in a diabetic rat model.

MATERIALS AND METHODS

Weight-matched adult male Wistar rats were grouped as control (n=8) and diabetic (n=8). In the latter group, diabetes was induced with a single intraperitoneal injection of 50 mg/kg streptozotosin. 72 hours after the injection, animals possessing a blood glucose concentration above 300 mg/kg were considered diabetic. The weights and blood glucose levels were observed for 7 days. In the end, 80 mg/kg ketamine and 12 mg/kg xylazine were administered to both groups, and the induction time of anesthesia was recorded. The success of anesthesia was confirmed with toe pinching by using a clamp. The Student's t- and Pearson's correlation tests were used for statistical analyses.

RESULTS

The induction time of anesthesia was significantly reduced in the diabetic group compared to the controls (p<0.01). Diabetic animals weighed less than the control group (p<0.01). The correlation analysis in the diabetic group showed that the weight and blood glucose level of animals did not influence the induction time of anesthesia (respectively, p=0.80, r: 0.150; p=0.68, r: -0.300). A negative correlation between blood glucose concentration and weight was found in diabetics (p<0.05, r: -0.828).

CONCLUSIONS

The dosage of anesthetic agents is important in the effectiveness of anesthesia, and surgical complications. Since our results indicate the susceptibility of diabetics to anesthesia, we suggest that the dose of anesthetics should be finely adjusted considering the presence of diabetes.

Alpha-lipoic acid could be a promising treatment in steroid-induced osteonecrosis

OBJECTIVE

Glucocorticoid-induced osteonecrosis is a serious debilitating health problem. In the present study, we investigated the effects of alpha-lipoic acid on glucocorticoid-induced osteonecrosis in rats.

MATERIALS AND METHODS

A total of 40 male Wistar albino rats were equally assigned to 4 groups as control, methylprednisolone acetate (MPA), alpha-lipoic acid (ALA), and methylprednisolone acetate with alpha-lipoic acid (MPA+ALA). The animals in MPA group subcutaneously received 15 mg/kg/week for 2 weeks, whereas 100 mg/kg/day alpha-lipoic acid was intraperitoneal administered for 4 weeks to ALA group. The MPA+ALA group was subjected to both treatments in same doses. Osteonecrosis was confirmed and graded histologically. The serum concentrations of glucose, total cholesterol, low- and high-density lipoprotein, triglyceride, as well as the total oxidant and antioxidant status, oxidative stress index, prothrombin time and activated partial thromboplastin time were evaluated. Also, lipid peroxidation and DNA damage were immunohistochemically assessed in the bone.

RESULTS

Osteonecrotic lesions were narrower in the MPA+ALA group than in the MPA group (p<0.05). As compared to the controls, the biochemical parameters in MPA and MPA+ALA groups were significantly increased (p<0.001). The oxidative stress index was significantly higher in the groups with MPA than the controls (p=0.002), but the animals treated with ALA alongside MPA displayed lesser scores than the ones injected with solely MPA (p=0.03). The administration of MPA elevated lipid peroxidation and DNA damage, which were successfully alleviated by ALA.

CONCLUSIONS

Alpha-lipoic acid may be suggested to be a protective supplement in glucocorticoid-induced osteonecrosis in rats. The antioxidant capacity of alpha-lipoic acid may involve its beneficial effects.

The endothelial nitric oxide synthase (eNOS) polymorphism in otitis media with effusion (OME)

OBJECTIVES

Otitis media with effusion (OME) is the most common disease after viral infections of upper respiratory tract (URTI) in children. Studies indicate the important role of nitric oxide (NO) in the etiology of hearing loss. However, there is no study that focuses on the role of nitric oxide synthase (eNOS) polymorphisms in the cases with OME. The aim of the present study is to evaluate the eNOS polymorphisms in the pediatric patients with OME.

MATERIALS AND METHODS

Eighty-nine patients who are diagnosed with otitis media with effusion and 85 healthy subjects who are compatible in terms of age and gender were included in the study. All patients in the study were subjected to complete ear, nose, throat (ENT) and audiological examinations. DNA analysis was performed with polymerase chain reaction (PCR) technique from the blood samples. The PCR product was cut by restriction fragment length polymorphism (RFLP) with BanII enzyme and checked by agarose gel electrophoresis.

RESULTS

As a result of genetic analysis, there is no significant difference between patients and the controls in terms of eNOS Glu298Asp polymorphism (G/G, G/T, T/T). When these groups were compared in terms of allele distributions, a significant relationship was found between the patients and the controls (P=0.037).

CONCLUSION

To the best of our knowledge, G allele was identified as predisposing to the development of OME and this is the first report indicates the correlation between the eNOS G894T polymorphism and OME in Turkey.

Elevated nucleosome level and oxidative stress in schizophrenia patients

AIM

The aim of this study was to investigate the effect of oxidative stress on nucleosome levels and its relation with the clinical features in schizophrenia patients.

MATERIAL AND METHOD

Thirty schizophrenia patients and 30 healthy controls were enrolled in this study. Patients were diagnosed with schizophrenia according to the 4th edition of the Diagnostic and Statistical Manual for Mental Disorders (DSM-IV). The control group consisted of 30 healthy subjects matched to the patients with regard to age and gender and who had no history of any psychiatric disorder. The severity of schizophrenia symptoms in the patients was evaluated using the Positive and Negative Syndrome Scale (PANSS) and the Clinical Global Impression Severity Scale (CGI-S). Physical and neurological examinations were performed in each of the patients and controls.

RESULTS

Nucleosome, total oxidant levels and OSI values were higher in schizophrenia patients than in controls (p<0.05). There was no significant difference in the total antioxidant levels. There was a positive correlation between the nucleosome level and PANSS positive subscale (p=0.028, r=0.402). There was a positive correlation between TAS and age (p=0.025, r=0.289), PANSS total (p<0.001, r=0.604). There was a negative correlation between OSI and PANSS total (p=0.019, r=-0.427), PANSS positive subscale (p=0.043, r=-0.372). There was a negative correlation between TOS and PANS total (p=0.028, r=-0.402).

CONCLUSION

In this study we found a correlation between nucleosome level and PANSS positive subscale. To our knowledge, this is the first study that evaluates oxidative stress and nucleosomes released from apoptotic cells together (Tab. 2, Ref. 50).