Dragomir Yankov is the Director of Institute of Chemical Engineering, Bulgarian Academy of Sciences. He joined the Institute as Research Fellow in 1984, where he received his PhD degree in 1998. Currently, he is a Professor in Chemical Engineering department. He has published more than 50 papers in reputed journals. He is a member of the Editorial Board of the Bulgarian Chemical Communications and Journal of Advanced Chemical Engineering.
Lactic acid is a useful chemical with both traditional (as acidulant, neutralizer and preservative) and newer (for environmentally friendly solvents or as precursor of biodegradable polymers) applications. Lactic acid can be manufactured by chemical synthesis or by fermentation of different carbohydrate materials by various microorganisms of Lactobacillaceae family. Lactobacillus plantarum is one of the most wide spread species used in lactic acid production by lactic acid bacteria. In the last years, the immobilization of whole lactobacillus cells attracts the attention of the researchers because of the undoubted advantages in lactic acid production. Various methods, belonging to all types of immobilization techniques, were used for immobilization of cells of the genus Lactobacillus. Spent grains originated from breweries and distilleries are the most abundant agro-industrial waste material and respond to most of the above listed requirements. Currently, spent grains are mainly used as animal feed. Attempts were made for using spent grains for extraction of metals and dyes. Greater attention was paid to the hydrolysis of the grains for producing fermentable sugars, used as substrates in various bioprocesses. A promising alternative for spent grains application is its use as carriers for enzymes and cells immobilization. The purpose of the present work is to investigate the applicability of distillers spent grains for cells immobilization, especially for the production of lactic acid. The immobilization was carried out by simultaneous growth and adhesion, adding spent grains in the beginning, before growth medium seeding at 30ºC for 24 h at gentle stirring. At the end, the concentration of free cells was determined, the support was separated from the broth, washed with sterile saline and kept at 4ºC in saline before further use. Influence of the particle size, pH, temperature and support treatment methods on the lactic acid fermentative production were examined. The immobilized preparation showed high activity (about 70-80% from free cells’ activity) and very good stability in at least two months repeated batch fermentations without pH control. There is no difference in optimal pH value and temperature for free and immobilized cells. The results obtained represent a good base for studying continuous lactic acid production.
Bohan Shan is a PhD student studying in Arizona State University, School for Engineering of Matter, Transport & Energy. He is working on synthesis and characterization of hydrostable MOFs in Dr. Bin Mu’s lab.
Metal-organic framework (MOFs) have attracted intensive attention in the past two decades. The high surface area, organized pore structure, and tailorable chemistry have made MOFs a promising series of candidates in chemical related applications, like gas separation and storage. The exploration of MOFs with desirable properties as well as high stability emerged as a research focus. We present the synthesis and characterization of a photoluminescent Zr-based MOF (ZrPDA) with controllable UV-induced structural variation, which can be potentially used in gas capture and storage. The high valence state Zr4+ and smart molecule, 1,4-phenylenediacrylic acid (H2PDA), which can go through [2+2] cycloaddition reaction under UV irradiation, were employed to form the ZrPDA. The structural variation of ZrPDA under UV exposure and its hydrostability were studied.