Production of (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer from coffee waste oil using engineered Ralstonia eutropha

Bioprocess and Biosystems Engineering - Polyhydroxyalkonate (PHA) is a type of polymer that has the potential to replace petro-based plastics. To make PHA production more economically feasible,...     

Effect of historical factors on genetic variation in three terrestrial Cephalanthera species (Orchidaceae) with different breeding system on the Korean Peninsula

Previous studies have shown that levels of genetic diversity in species of the genus Cephalanthera covary with the breeding system. In the southern part of the Korean Peninsula, the three self‐compatible terrestrial orchids Cephalanthera erecta, C. falcata and C. longibracteata flower synchronously in sympatric populations. The food‐deceptive C. falcata with bright yellow flowers is predominantly outcrossing, whereas autogamy is the dominant strategy in both C. erecta and C. longibracteata, whose white flowers do not open fully. We examined genetic diversity (by means of allozymes) of the three species in sympatric populations (600 × 600 m area) in the Yeonwhasan Provincial Park (YPP) and in non‐sympatric populations outside YPP, South Korea. Thirteen out of 20 putative loci were variable across the three species, but there was a complete lack of allozyme variation within each species and we found no evidence of hybridisation. Our results suggest that historical factors, i.e. the Quaternary climate oscillations, have played a major role in determining levels of genetic diversity in the three Cephalanthera species. The Korean populations of C. erecta (a warm‐temperate/temperate element) and C. falcata (a warm‐temperate element) may have been established by a single introduction from a genetically depauperate ancestral population, likely located outside the Korean Peninsula. On the other hand, since C. longibracteata is a boreal/temperate element, it may have survived the Last Glacial Maximum in microrefugia located in low elevation regions within the Peninsula where it has been subjected to population bottlenecks reducing its genetic diversity.     

Morphological and random amplified polymorphic DNA features in populations ofCeramium kondoi (Rhodophyta)

Morphological and RAPD features ofCeramium kondoi populations were investigated and compared in different locations in Korea. The plant length and branching pattern were more variable in Jindo population than others. RAPD data showed thatC. kondoi plants were divided into two clades; the southern group including Jindo and Bangpo population, and the northern group including Yonpyongdo and Oeyondo population. Morphological features inC. kondoi populations corresponded with RAPD data, which differed from those ofC. boydenii from the same location. These results suggest that RAPD might be useful for elucidating genetic variation among the wild populations ofC. kondoi.     

Suppression of acidogenic activities due to rapid temperature drop in anaerobic digestion

A rapid temperature drop during anaerobic acidogenesis in an anaerobic reactor system resulted in the sharp suppression of carbohydrate decomposition and production of volatile fatty acids. When the temperature was dropped from 30°C to 25, 20, 15°C sequentially, the numbers of bacteria were slowly reduced without showing temperature shock. The acidogenesis, however, was dramatically affected after each temperature drop; the removal efficiency of carbohydrate was reduced from 92% to 84%, 72%, 25% with showing the minima of 78%, 52% and 10% due to the rapid temperature drop respectively. This indicates that the acidogens lose the activities momentarily during the rapid temperature drop and require certain period of time to recover the activities at the adjusted fermentation temperature. This revised version was published online in November 2006 with corrections to the Cover Date.     

Optimization of operating variables for polyphenol extraction from lipid-extracted microalgae using acid-catalyzed hot-water extraction

Microalgae are a promising source of lipids for biodiesel production, which has the potential to replace fossil fuels without affecting the supply of foods and crop products. From the production of biodiesel, a solid waste known as lipid-extracted microalgae (LEM) is generated as a byproduct, and it is considered a rich source of antioxidant compounds, mainly polyphenols. In this study, optimization of the process variables of acid-catalyzed hot-water extraction was performed at low temperature in order to increase the production of polyphenols from LEM (Tetraselmis KCTC 12236BP). A statistically based method was used to optimize key variables, including extraction temperature, time, and sulfuric acid concentration. The results indicated that all process variables had significant effects on the extraction of polyphenols (p < 0.05). For instance, polyphenol levels increased in accordance with the increase of the three variables. The most economical optimal conditions were 100°C, 46.8 min, and 0.32 N H₂SO₄, under which polyphenol yield was 8.04 mg gallic acid equivalent (GAE)/g dry matter (DM), 5.2-fold higher than that from hot-water extraction without optimization.     

Recent Developments of the Lithium Metal Anode for Rechargeable Non‐Aqueous Batteries

Over the last 40 years, metallic lithium as an anode material has been of great interest owing to its high energy density. However, dendritic lithium growth causes serious safety issues. Awareness and understanding of the Li deposition and stripping processes have grown rapidly especially in recent years, and consequently, there have been many attempts to suppress the Li dendrites. Recent developments that have modified the electrolytes and the Li anode in order to inhibit the growth of Li dendrite and improve cycling performance are summarized. It has been shown that current density, solid‐electrolyte interphase (SEI) film, Li⁺ transference number, and shear modulus have significant impact on the growth behavior and the Coulombic efficiency. Various methods have been introduced to increase the surface area of the Li anode, enhance Li⁺ conductivity, form stable SEI film, and improve mechanical strength of electrolytes. These approaches are discussed in details, and the perspectives regarding the future use of Li anode are also outlined. It is hoped that this review will facilitate the future development of Li metal batteries.