K.Tanaka has completed his PhD at the age of 31 years from Kyushu University. He is a professor of Dept. Biological and Environmental Chemistry, Sch.Humanity-Oriented Science & Engineering, Kindai University. His research field is bioprocess engineering. He has published many papers for microbial production of biodegradable plastic from CO2 and biomass.
Poly((R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate) [P(3HB-co-3HHx)], a flexible and practical biodegradable plastic, is generally produced from plant oils and fatty acids by several wild and recombinant bacteria. Fukui and his coworkers constructed many recombinants of Ralstonia eutropha for studying biosynthesis of [P(3HB-co-3HHx)] with high 3HHx composition from the structurally unrelated carbon source. The engineered strain with ΔphaB1 genotype expressing ccr, phaJ4a, and emd (R.eutropha strain MF01ΔB1/pBPP-ccrMeJ4a-emd) produced P (3HB-co-3HHx) composed of 22 mol% 3HHx at high cellular content from fructose (Metabolic Engineering, 27:38–45, 2015). Such high C6–monomer composition was achieved by improving artificial pathway for biosynthesis of monomer unit as follows:- (i) depression of (R)-specific reduction of acetoacetyl-CoA by the deletion of phaB1 for formation of the C6–monomer unit from fructose driven by crotonyl-CoA carboxylase/reductase (Ccr) (ii) Co-overexpression of phaJ4a, which encodes medium-chain-length (R)-enoyl-CoA hydratase, with ccr promoted the incorporation of both 3HB and 3HHx units (iii) introduction of emdMm, a synthetic gene encoding ethylmalonyl-CoA decarboxylase derived from mouse which is probably converting ethylmalonyl-CoA generated by the reductive carboxylase activity of Ccr back into butyryl-CoA. R.eutropha is a facultative hydrogen-oxidizing bacterium that chemolithoautotrophically grows due to carbon dioxide fixation using H2 and O2 as the energy source. Hence, we also investigated the production of P(3HB-co-3HHx) from CO2 by the engineered strains of R.eutropha in chemolithoautotrophic condition using the substrate gas mixture (H2/O2/CO2=8:1:1) and mineral salts medium. As a result, the strain MF01ΔB1/pBPP-ccrMeJ4a-emd produced P(3HB-co-3HHx) with a remarkably high composition of 3HHx (51.7mol%) at a high cellular content (65.1wt%) from CO2.
M.C. Veiga obtained her PhD in the field of environmental bioengineering at the University of Santiago de Compostela. Afterwards she had a postdoctoral position at Michigan State University. At present she coordinates the Environmental Engineering Group at University of A Coruña. Main research interests are on the development of sustainable processes for the removal of pollutants from wastewater and production of biopolymers from renewable sources.
Food wastes are produced in large quantities in markets, intensive production areas and in canned vegetable companies. Solid waste generation from these companies is a major source of pollution in landfills where they are deposited and have many environmental problems associated. An efficient alternative to prevent this accumulation is the re-valorisation through acidogenic fermentation to produce volatile fatty acids (VFA), precursors for the production of polyhydroxyalkanoates (PHAs). In this work five different types of wastes were used: potato solids from a chips factory, salad from vegetable factory and three wine wastes generated in different stages of winemaking process. The diversity of these wastes related with their origin, composition and production period needs to be studied separately. In a batch experiment were compared all of them to evaluate VFAs productivity and distribution. The highest yield was reached with potato solids (0,8 g VFA/ g VS waste), salad waste (0,75 g VFA/ g VS waste) and marc grape (0,7 g VFA/ g VS waste). The VFA profile showed acetic and butyric as predominant acids in the potato and salad wastes. In the case of two wine substrates produced in different stages of distillery wine, the degree of acidification was lower than 0,25 g VFA/ g VS waste added. The predominant acids were acetic and propionic in all of wine wastes. These results will help to optimize the acidogenic fermentation of each particular waste and to stablish a new strategy for their co-digestion. Acknowledgements: The present research was financed through project CTQ2013-45581-R from the Spanish Ministry of Economy and Competitiveness.