Direct bioelectrocatalysis at the interfaces by genetically engineered dehydrogenase

This is the published version.There is an emerging interest in developing bio-functionalisation routes serving as platforms for assembling diverse enzymes onto material surfaces. Specifically, the fabrication of next-generation, laboratory-on-a-chip-based sensing and energy harvesting systems requires controlled orientation and organisation of the proteins at the inorganic interfaces. Herein, the authors take the initial steps towards designing multifunctional, enzyme-based platforms by genetically integrating the engineered materialselective peptide tags for tethering redox enzymes onto electrode surfaces. The authors engineered a fusion protein that genetically conjugates gold-binding peptide to formate dehydrogenase derived from Candida methylica. The expressed proteins were tested for both enzyme activity and self-directed gold-surface functionalisation ability. Their findings demonstrate the successful self-immobilisation of the engineered enzyme onto different gold electrodes while retaining the catalytic activity. Building on the functionalisation by the peptides, a fusion enzyme-integrated circuit-based biosensor system was designed. The catalytic conversion of the formate by the engineered dehydrogenase was successfully monitored on the electrode surface at subsequent intervals. The engineered peptide-mediated self-integrated electrode systems can be extended to develop a wide range of biosensing and energy-harvesting platforms using different combinations of materials and biomolecules. This paper contains supporting information that will be made available online once the issue is published. In the meantime, if you wish to get a copy of the supplementary file, please contact the Journals Editor, Sarah Brown, at [email protected]

Preparation of Bacterial Cellulose Using Enzymatic Hydrolysate of Olive Pomace as Carbon Source

Bacterial cellulose has superior physical and chemical properties, biocompatibility, and purity. However, the high production cost obstructs the common use of this polymer. This study investigated the efficiency of olive pomace, an important by-product of olive oil industry in Turkey, as a carbon source for Novacetimonas hansenii. Olive pomace pretreatment with 1% H3PO4 was followed by enzymatic hydrolysis. The maximal reducing sugar concentration upon enzymatic process was 9.3 g/L with 1 enzyme: 6 substrate (dry matter) ratio. After incubation in the growth media prepared with the obtained reducing sugar as carbon source, the highest bacterial cellulose production was 0.68 g/L. Structural analysis indicated that bacterial cellulose from the enzymatic media and the conventional Hestrin-Schramm medium possess similar characteristics. The present work provides a favourable method to reduce the cost of bacterial cellulose production

Biogeochemistry of Balikesir Balya Pb-Zn Mine Tailings Site and Its Effect On Generation of Acid Mine Drainage

Biogeochemical characteristsics of Balikesir-Balya Pb-Zn Mine Waste site, known as the oldest and largest mine tailing site in Turkey, and its influence on generation of acid mine drainage was investigated by geochemical, molecular and microbiological approach. The oxidation of sulfide rich rocks and waste, mostly left over from Balya Pb-Zn mining activities, is generating acidic water with low pH (2.7), and contributing to metal contamination containing up to 1.88 mg/L Pb, 24 mg/L Zn, 2.5 mg/L As ve 17 mg/L Cu. Geochemical and molecular/microbiological analysis on mine waste, sediment and water samples (acidic, surface) show that acidic surface waters generated from sulfide weathering are principal pathways for mobility and redistribution of environmentally important elements into the environments. Based on cultivation based microbiological analysis carried out on acidic ponds developed around and in Balya Mine waste sites, the mean acidofilic sulfur oxidizing bacteria (aSOB) and acidophilic iron oxidizing bacteria were determined as 8.4x10(8)cell/ml ve 9.6x10(7) cell/ml, respectively. The relatively low values for surface water of Maden creek, where mine wastes reach, were determined as 3.8x10(6) cell/ml ve 5.7x10(3) cell/ml, respectively. Molecular analysis of 16S rDNA gene sequences from acidic sediment and sediment from Maden Creek show the dominance of S and Fe-oxidizing prokaryotes belonging to Acidithiobacillus spp. genus in the primary drainage communities. Relatively small populations of Sulfobacillus spp. were also determined. Moreover, species belong to Thiobacillus spp. and Thiovirga spp. genus were only determined on the sediment samples from Maden creek with low acidity relative to acidic sediment. These sulfur oxidizer indicates a dynamic microbial population which adapt to changing geochemical conditions. Identification of Fe oxidizer and reducer along with Jarosite, plumbojarosite and goethite in the sediments of acidic ponds indicate significance of microbial Fe cycle governing mobilization and redistribution of the metals in the waste site. Overall, it is shown that microorganisms regulating S and Fe cycle in Balya mine waste site is the key factors controlling generation and chemistry of acidic drainage water

Peptides to bridge biological-platinum materials interface

Peptides with inorganic materials recognition already started to impact a wide range of surface- related technologies ranging from biomonitoring to biomedical areas. Combinatorial biology- based libraries are the initial step in tempting the directed evolution of peptides with specifi c interactions towards technologically relevant materials. Here, a case study is provided to demonstrate the specifi c peptide binding and the amino acids residues that play an important role for platinum surface affi nity by combining computational as well as genetic engineering tools. Using a phage display technique, septapeptides were identifi ed exhibiting affi nity to noble metal platinum, and the amino acid distributions in the identifi ed peptides were analyzed. The analysis of the peptide sequences showed that strong Pt- binding peptides contain positively charged, hydrophilic, and polar residues, and especially enriched in threonine, serine, and glutamine. Under competitive surface- binding conditions, strong Pt- binding peptide motif displayed on phage resulted in high specifi city to Pt regions on a Pt- macropatterned glass. Conformational analysis of the strong binder indicates that threonine and serine as well as glutamine are in close contact with the surfaces forming a tripod molecular architecture. The alanine substitution mutagenesis applied at the genomic level to the peptide displayed on the phage revealed threonine and serine substitutions as the critical ones. Understanding the residue- based interactions of the peptide sequences can be utilized to tune the affi nity and the specifi city of the peptides with the inorganic surfaces, toward making them indispensable molecular tools to control the molecular interactions of biological macromolecules with the material surfaces