Haruhiko Yokoi

Some taxonomical characteristics of encapsulated Lactobacillus sp. KPB-167B isolated from kefir grains and characterization of its extracellular polysaccharide.

A capsular polysaccharide-producing strain KPB-167B isolated from kefir grains was identified as a homofermentative Lactobacillus. The carbohydrate fermentation pattern and DNA base composition of the strain were different from those of other capsular Lactobacillus species previously isolated from kefir grains. The polysaccharide produced by Lactobacillus sp. KPB-167B was found similar to kefiran by 13C-NMR and methylation analysis. Lactobacillus sp. KPB-167B could grow and produce capsular polysaccharide in MRSL medium with better yield than L. kefiranofaciens, which suggested that it is suitable for kefiran production.

High density cultivation of plant cells in a new aeration-agitation type fermentor, Maxblend Fermentor®

Abstract The applicability of a new aeration-agitation type fermentor with a grid-paddle type impeller and a spiral-sparger, Maxblend Fermentor® (MBF) for high density cultivation of plant cells, was investigated. The MBF showed a high capacity for oxygen supply and extremely low hydrodynamic stress in aeration and mixing compared with a conventional fermentor (CF). When Oryza sativa cells were cultivated at a k L a of 20 h −1 , a high cell density cultivation of about 30 g dry cell weight per liter was accomplished in both fermentors and there were few differences in culture performance between the two. On the contrary, considerable differences were observed when Catharanthus roseus cells, which seemed to be sensitive to physical stress, were cultivated at a k L a of 20 h −1 in both fermentors. The MBF exhibited excellent cell growth characteristics, achieving about 19 g dry cell weight per liter, because of its superior oxygen supply and low hydrodynamic stress in aeration and mixing in highly viscous cultures containing high density cells. In CF only about 9.5 g dry cell weight per liter was achieved because of its high hydrodynamic stress.

Optimum Culture Conditions for Production of Kefiran by Lactobacillus sp. KPB-167B Isolated from Kefir Grains

Abstract Optimum culture conditions for the effective production of kefiran, a water-soluble polysaccharide, by Lactobacillus sp. KPB-167B isolated from kefir grains were examined. Kefiran could be produced under conditions where cell growth was observed. The pH controlled at 5.0 and the temperature at 30°C were favorable for kefiran production. The highest yield of 2.04 g/ l in broth was accomplished in a modified MRSL medium contained 10% lactose, 5 mM CaCl 2 and two-fold the original nitrogen sources for 4 d. In a modified MW (milk whey) medium with additional 5% lactose and two-fold the original nitrogen sources, 0.60 g/ l of kefiran were obtained for 5 d.

An Application of a Bioreactor with Flocculated Cells of Halophilic Micrococcus Varians Subsp. Halophilus Which Preferentially Adsorbed Halophilic Nuclease H to 5’-Nucleotide Production

A bioreactor system was designed with the flocculated cells of halophilic Micrococcus varians subsp. halophilus which immobilized halophilic nuclease H on the surface, for the production of flavouring agent, 5’-guanylic acid (5’-GMP). As the bacterium produced an extracellular 5’-nucleotidase as well as the nuclease H, selective inactivation of the 5’-nucleotidase contaminated in the column was necessary to obtain high yields of 5’-GMP from RNA. A fact that the exogenous nuclease H was preferentially adsorbed on the flocculated cells over the 5’-nucleotidase was advantageous to the production. Desalting treatment of the flocculated cells in the presence of 80 mM MgSO4 preferentially inactivated 5’-nucleotidase, and the RNA degradation in the presence of 0.25 mM ZnSO4 greatly improved the yield. Furthermore, Ca-enzyme-complex which was formed by adding CaC12 to the supernatant of the culture at 25°C was applied to the bioreactor.

Effects of lipids and related compounds on the production of halophilic 5′-nucleotidase and nuclease H by a moderate halophile, Micrococcus varians subsp. halophilus

Abstract The effects of lipids and related compounds on the production of halophilic 5′-nucleotidase and nuclease H by a moderate halophile, Micrococcus varians subsp. halophilus were examined. In order to increase the yield of flavoring 5′-nucleotide production from RNA using crude enzyme solution containing 5′-nucleotidase as well as nuclease H, the selective prevention of 5′-nucleotidase production is necessary. Addition of 0.5 to 1.0% whale oil was found to be fairly effective for the purpose, giving about 72 to 84% prevention. Tripalmitin, triolein and ethyllaurate also showed similar high levels of selective prevention. As it is known that whale oil contains relatively high percentages of palmitate and oleate, its effect seems to be partly attributable to the high content of these esters.