During light induction for astaxanthin formation in Haematococcus pluvialis, we substituted photoautotrophic induction for heterotrophic induction using acetate, both to prevent contamination by heterotrophs due to addition of organic carbon and to enhance carbon assimilation in the induced cells. Strong photoautotrophic induction was performed by N-deprivation of photoautotrophically grown Haematococcus cells followed by supplementation with bicarbonate (HCO(3)(-)) or CO(2). Bicarbonate-induced cells contained more astaxanthin than acetate-induced cells, and even further enhancement of astaxanthin accumulation was achieved by continuous CO(2) supply. The maximum astaxanthin content (77.2 mg g(-1) biomass, 3.4-fold higher than with heterotrophic induction) was obtained under conditions of 5% CO(2), yielding astaxanthin concentration and productivity of 175.7 mg l(-1) and 6.25 mg l(-1) day(-1), respectively. The results indicate that photoautotrophic induction is more effective than heterotrophic induction for astaxanthin synthesis in H. pluvialis.

We investigated the effect of carbon/nitrogen (C/N) ratio on astaxanthin synthesis in Haematococcus pluvialis during photoautotrophic induction by continuous input of both CO(2)-air mixture and intense light. When H. pluvialis was induced by constant irradiance induction at 200 micromol photon m(-2) s(-1), there was a positive correlation with astaxanthin content and C/N ratio, which was similar to the case for heterotrophic induction. Lower C/N ratios did not retard Haematococcus encystment, but did increase culture biomass, resulting in a decrease in astaxanthin production because of light limitation. However, induction using variable irradiance showed that reduction of astaxanthin production at low C/N ratios was successfully overcome by simply increasing the light intensity from 200 to 300 micromol photon m(-2) s(-1) to overcome the light limitation. This resulted in a greatly enhanced astaxanthin synthesis in proportion to cell density in cultures with low C/N ratios. Our results indicate that light intensity is more critical than C/N ratio in astaxanthin production by H. pluvialis during photoautotrophic induction.

We demonstrate the fabrication of nanoelectromagnets and the magnetic capture of a single magnetic nanoparticle. The magnetic nanoparticles are extracted from magnetotactic bacteria and their diameter is approximately 50 nm. We show that a single nanoparticle is captured at each corner of the serpentine-shaped nanoelectromagnet, and the maximum magnetic field of 35 mT ͑and the maximum magnetic-field gradient of 4 ϫ 10 5 T/m͒ is shown to be created at the capture spots of the nanoelectromagnet. It is also shown that there is a crossover between the magnetic force and the diffusion force at several hundred nm away from the magnet. This distance is comparable to the average interparticle distance.

Q ) mutant phage k is de®cient in the synthesis of the proteins involved in cell lysis and k DNA packaging. As a result, the replicated Q ) k DNA containing a cloned gene is not easily coated by a phage head and remains naked for the ample expression of the cloned gene, and also the host cells do not lyse easily and larger amounts of cloned gene products are produced. In a two-phase operation, the ®rst phase is operated at a low temperature to keep the phage in the lysogenic state for cell growth and cloned gene stability, while the second phase is operated at a high temperature to induce the lytic state for the am-pli®cation of the cloned gene and overproduction of its product. This two-phase operation was optimized by determining both the optimal temperatures for the growth and production phases and the optimal switching time between the growth to the production phase. The optimal temperatures for growth and production phases were 33 and 40°C, respectively. The optimal switching time was 3 h. The recombinant b-galactosidase production using this optimal process was about 20 times higher than in the single-copy lysogenic state.

Amino acids rather than sugars are the primary limiting substrates for the culture of insect cells in a Grace's medium. When cultures are supplemented with amino acids, the yeastolate components other than the amino acids become the secondary limiting substrates. For the fed-batch culture of insect cells, a solution containing concentrated amino acids and yeastolate was supplied using an exponential feed¯ow rate calculated from mass balance equations. During the batch period the speci®c growth rate was 0.02 h )1 , whereas during the fed-batch period it was measured as 0.007 and 0.012 h )1 on the basis of the cell numbers and the dry cell weight, respectively. This difference in the speci®c growth rates in the fed-batch period is caused by an increase in the cell size during this period. Furthermore, in fed-batch cultures, dissolved oxygen was found to be a limiting factor for high cell-density cultures.