Biosynthesis of functional polyhydroxyalkanoates by engineered Halomonas bluephagenesis.

Polyhydroxyalkanoates (PHA) have found widespread medical applications due to their biocompatibility and biodegradability, while further chemical modification requires functional groups on PHA. Halomonas bluephagenesis, a non-model halophilic bacterium serving as a chassis for the Next Generation Industrial Biotechnology (NGIB), was successfully engineered to express heterologous PHA synthase (PhaC) and enoyl coenzyme-A hydratase (PhaJ) from Aeromonas hydrophila 4AK4, along with a deletion of its native phaC gene to synthesize the short chain-co-medium chain-length PHA copolymers, namely poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhex-5-enoate) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyhex-5-enoate). After optimizations of the expression cassette and ribosomal binding site combined with introduction of endogenous acyl-CoA synthetase (fadD), the resulting recombinant strain H. bluephagenesis TDR4 achieved a remarkably high 3-hydroxyhexenoate (3HHxE) molar ratio of 35% when grown on glucose and 5-hexenoic acid as co-substrates. The total ratio of side chain consisting of 3HHx and 3HHxE monomers in the terpolymer can approach 44 mol%. H. bluephagenesis TDR4 was grown to a cell dry mass (CDM) of 30 g/L containing approximately 20% poly(3-hydroxybutyrate-co-22.75 mol% 3-hydroxy-5-hexenoate) in a 48-h of open and unsterile fermentation with a 5-hexenoic acid conversion efficiency of 91%. The resulted functional PHA containing 12.5 mol% 3-hydroxy-5-hexenoate exhibits more than 1000% elongation at break. The engineered H. bluephagenesis TDR4 can be used as an experimental platform to produce functional PHA.

The tae-miR408-Mediated Control of TaTOC1 Genes Transcription Is Required for the Regulation of Heading Time in Wheat.

Timing of flowering is not only an interesting topic in developmental biology, but it also plays a significant role in agriculture for its effects on the maturation time of seed. The hexaploid wheat (Triticum aestivum) is one of the most important crop species whose flowering time, i.e. heading time, greatly influences yield. However, it remains unclear whether and how microRNAs regulate heading time in it. In our current study, we identified the tae-miR408 in wheat and its targets in vivo, including Triticum aestivum TIMING OF CAB EXPRESSION-A1 (TaTOC-A1), TaTOC-B1, and TaTOC-D1. The tae-miR408 levels were reciprocal to those of TaTOC1s under long-day and short-day conditions. Wheat plants with a knockdown of TaTOC1s via RNA interference and overexpression of tae-miR408 showed early-heading phenotype. Furthermore, TaTOC1s expression was down-regulated by the tae-miR408 in the hexaploid wheat. In addition, other important agronomic traits in wheat, such as plant height and flag leaf angle, were regulated by both tae-miR408 and TaTOC1s. Thus, our results suggested that the tae-miR408 functions in the wheat heading time by mediating TaTOC1s expression, and the study provides important new information on the mechanism underlying heading time regulation in wheat.

Open and continuous fermentation: products, conditions and bioprocess economy.

Microbial fermentation is the key to industrial biotechnology. Most fermentation processes are sensitive to microbial contamination and require an energy intensive sterilization process. The majority of microbial fermentations can only be conducted over a short period of time in a batch or fed-batch culture, further increasing energy consumption and process complexity, and these factors contribute to the high costs of bio-products. In an effort to make bio-products more economically competitive, increased attention has been paid to developing open (unsterile) and continuous processes. If well conducted, continuous fermentation processes will lead to the reduced cost of industrial bio-products. To achieve cost-efficient open and continuous fermentations, the feeding of raw materials and the removal of products must be conducted in a continuous manner without the risk of contamination, even under 'open' conditions. Factors such as the stability of the biological system as a whole during long cultivations, as well as the yield and productivity of the process, are also important. Microorganisms that grow under extreme conditions such as high or low pH, high osmotic pressure, and high or low temperature, as well as under conditions of mixed culturing, cell immobilization, and solid state cultivation, are of interest for developing open and continuous fermentation processes.

Determination of light-medium-heavy polycyclic aromatic hydrocarbons in vegetable oils by solid-phase extraction and high-performance liquid chromatography with diode array and fluorescence detection.

A new method for determination of 16 polycyclic aromatic hydrocarbons (PAHs)-naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene, and indeno[1,2,3-cd]pyrene-in vegetable oils was developed. Solid-phase extraction (SPE) prior to high-performance liquid chromatography with fluorescence detection could be used for all those PAHs except acenaphthylene. Acenaphthylene could be detected using a diode array detector at 228 nm. The parameters and variables that affect the extraction were investigated. Under optimum conditions: the extract reagent was centrifuged at 4 °C and evaporated. After that a SPE procedure was used for further cleanup. The limits of detection and limits of quantification were in the range of 0.01-2.35 and 0.04-7.00 µg kg(-1) in vegetable oil, respectively. The relative standard deviations were under 5%.