Complete chloroplast genome of Sphagnum subsecundum Nees from Korea.

We determined the complete chloroplast genome sequence of the peatmoss Sphagnum subsecundum Nees from Mt. Halla in Korea. The total size of the chloroplast genome was 140,136 bp, and it consisted of a large single-copy region (LSC) of 98,064 bp, a small single-copy region (SSC) of 21,388 bp, and two copies of inverted repeat (IRa and IRb) regions of 10,342 bp each. The genome encoded a set of 130 genes, comprising 85 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. This species formed a monophyletic clade with S. orientale and S. lenese as the result of ML phylogenetic analysis based on whole gemone sequence of 15 species including one outgroup species.

A feasible enzymatic process for D-tagatose production by an immobilized thermostable L-arabinose isomerase in a packed-bed bioreactor.

To develop a feasible enzymatic process for d-tagatose production, a thermostable l-arabinose isomerase, Gali152, was immobilized in alginate, and the galactose isomerization reaction conditions were optimized. The pH and temperature for the maximal galactose isomerization reaction were pH 8.0 and 65 degrees C in the immobilized enzyme system and pH 7.5 and 60 degrees C in the free enzyme system. The presence of manganese ion enhanced galactose isomerization to tagatose in both the free and immobilized enzyme systems. The immobilized enzyme was more stable than the free enzyme at the same pH and temperature. Under stable conditions of pH 8.0 and 60 degrees C, the immobilized enzyme produced 58 g/L of tagatose from 100 g/L galactose in 90 h by batch reaction, whereas the free enzyme produced 37 g/L tagatose due to its lower stability. A packed-bed bioreactor with immobilized Gali152 in alginate beads produced 50 g/L tagatose from 100 g/L galactose in 168 h, with a productivity of 13.3 (g of tagatose)/(L-reactor.h) in continuous mode. The bioreactor produced 230 g/L tagatose from 500 g/L galactose in continuous recycling mode, with a productivity of 9.6 g/(L.h) and a conversion yield of 46%.

Continuous D-tagatose production by immobilized thermostable L-arabinose isomerase in a packed-bed bioreactor.

D-Tagatose was continuously produced using thermostable L-arabinose isomerase immobilized in alginate with D-galactose solution in a packed-bed bioreactor. Bead size, L/D (length/diameter) of reactor, dilution rate, total loaded enzyme amount, and substrate concentration were found to be optimal at 0.8 mm, 520/7 mm, 0.375 h(-1), 5.65 units, and 300 g/L, respectively. Under these conditions, the bioreactor produced about 145 g/L tagatose with an average productivity of 54 g tagatose/L x h and an average conversion yield of 48% (w/w). Operational stability of the immobilized enzyme was demonstrated, with a tagatose production half-life of 24 days.