Visible light photocatalytic disintegration of waste activated sludge for enhancing biogas production.

Biogas production using waste activated sludge (WAS) is one of the most demanding technologies for sludge treatment and generating energy in sustainable manner. The present study deals with the photocatalytic pretreatment of WAS using ZnO-ZnS@polyaniline (ZnO-ZnS@PANI) nanocomposite as means for increasing its degradability for improved biogas production by anaerobic digestion (AD). Photocatalysis accelerated the hydrolysis of WAS and increased the sCOD by 6.7 folds after 6 h and transform tCOD into bioavailable sCOD. After the AD of WAS, a removal of organic matter (60.6%) and tCOD (69.3%) was achieved in photocatalytic pretreated sludge. The biogas production was 1.6 folds higher in photocatalytic sludge with accumulative biogas up to 1645.1 ml L-1vs after 45 days compared with the raw sludge (1022.4 ml L-1VS). Moreover, the photocatalysis decrease the onset of methanogenesis from 25 to 12 days while achieve the maximum conversion rate of reducing sugars into organic acids at that time. These results suggested that photocatalysis is an efficient pretreatment method and ZnO-ZnS@PANI can degrade sludge efficiently for enhance biogas production in anaerobic digestion process.

Saccharification and hydrolytic enzyme production of alkali pre-treated wheat bran by Trichoderma virens under solid state fermentation.

BACKGROUND: In continuation of our previously interest in the saccharification of agriculture wastes by Bacillus megatherium in solid state fermentation (SSF), we wish to report an investigation and comparative evaluation among Trichoderma sp. for the saccharification of four alkali-pretreated agricultural residues and production of hydrolytic enzymes, carboxymethyl cellulase (CMCase), filter paperase (FPase), pectinase (PGase) and xylanase (Xylase) in SSF. The optimization of the physiological conditions of production of hydrolytic enzymes and saccharification content from Trichoderma virens using alkali-pretreated wheat bran was the last goal. METHODS: The physico-chemical parameters of SSF include incubation time, incubation temperature, moisture content of the substrate, incubation pH, supplementation with carbon and nitrogen sources were optimized. RESULTS: Saccharification of different solid state fermentation sources wheat bran, date's seeds, grass and palm leaves, were tested for the production of fermentable sugar by Trichoderma sp. The maximum production of hydrolytic enzymes CMCase, FPase, PGase and Xylase and saccharification content were obtained on wheat bran. Time course, moisture content, optimum temperature, optimum pH, supplementation with carbon and nitrogen sources were optimized to achieve the maximum production of the hydrolytic enzymes, protein and total carbohydrate of T. virens using alkali pre-treated wheat bran. The maximum production of CMCase, FPase, PGase, Xylase, protein and carbohydrate content was recorded at 72 h of incubation, 50-70 % moisture, temperature 25-35 °C and pH 5. The influence of supplementary carbon and nitrogen sources was studied. While lactose and sucrose enhanced the activity of PGase from 79.2 to 582.9 and 632.6 U/g, starch inhibited all other enzymes. This was confirmed by maximum saccharification content. Among the nitrogen sources, yeast extract and urea enhanced the saccharification content and CMCase, PGase and Xylase. CONCLUSIONS: The results of this study indicated that alkali pre-treated wheat bran was a better substrate for saccharification and production of hydrolytic enzymes CMCase, FPase, PGase and xylase by T. virens compared to other alkali-pretreated agricultural residues tested.

Solid fermentation of wheat bran for hydrolytic enzymes production and saccharification content by a local isolate Bacillus megatherium.

BACK GROUND: For enzyme production, the costs of solid state fermentation (SSF) techniques were lower and the production higher than submerged cultures. A large number of fungal species was known to grow well on moist substrates, whereas many bacteria were unable to grow under this condition. Therefore, the aim of this study was to isolate a highly efficient strain of Bacillus sp utilizing wheat bran in SSF and optimizing the enzyme production and soluble carbohydrates. RESULTS: A local strain Bacillus megatherium was isolated from dung sheep. The maximum production of pectinase, xylanase and α-amylase, and saccharification content (total soluble carbohydrates and reducing sugars) were obtained by application of the B. megatherium in SSF using wheat bran as compared to grasses, palm leaves and date seeds. All enzymes and saccharification content exhibited their maximum production during 12-24 h, at the range of 40-80% moisture content of wheat bran, temperature 37-45°C and pH 5-8. An ascending repression of pectinase production was observed by carbon supplements of lactose, glucose, maltose, sucrose and starch, respectively. All carbon supplements improved the production of xylanase and α-amylase, except of lactose decreased α-amylase production. A little increase in the yield of total reducing sugars was detected for all carbon supplements. Among the nitrogen sources, yeast extract induced a significant repression to all enzyme productivity. Sodium nitrate, urea and ammonium chloride enhanced the production of xylanase, α-amylase and pectinase, respectively. Yeast extract, urea, ammonium sulphate and ammonium chloride enhanced the productivity of reducing sugars. CONCLUSIONS: The optimization of enzyme production and sccharification content by B. megatherium in SSF required only adjustment of incubation period and temperature, moisture content and initial pH. Wheat bran supplied enough nutrients without any need for addition of supplements of carbon and nitrogen sources.

Neuroprotective Mechanisms Mediated by CDK5 Inhibition.

Cyclin-dependent kinase 5 (CDK5) is a proline-directed serine/threonine kinase belonging to the family of cyclin-dependent kinases. In addition to maintaining the neuronal architecture, CDK5 plays an important role in the regulation of synaptic plasticity, neurotransmitter release, neuron migration and neurite outgrowth. Although various reports have shown links between neurodegeneration and deregulation of cyclin-dependent kinases, the specific role of CDK5 inhibition in causing neuroprotection in cases of neuronal insult or in neurodegenerative diseases is not wellunderstood. This article discusses current evidence for the involvement of CDK5 deregulation in neurodegenerative disorders and neurodegeneration associated with stroke through various mechanisms. These include upregulation of cyclin D1 and overactivation of CDK5 mediated neuronal cell death pathways, aberrant hyperphosphorylation of human tau proteins and/or neurofilament proteins, formation of neurofibrillary lesions, excitotoxicity, cytoskeletal disruption, motor neuron death (due to abnormally high levels of CDK5/p25) and colchicine- induced apoptosis in cerebellar granule neurons. A better understanding of the role of CDK5 inhibition in neuroprotective mechanisms will help scientists and researchers to develop selective, safe and efficacious pharmacological inhibitors of CDK5 for therapeutic use against human neurodegenerative disorders, such as Alzheimer's disease, amyotrophic lateral sclerosis and neuronal loss associated with stroke.