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.

A green, downstream process using common vegetable oils was used for the direct extraction of astaxanthin from Haematococcus. The process consists of a single integrated unit to extract astaxanthin with subsequent separation of the astaxanthin-containing oil extract. Without a cell harvest process step, the culture broth was directly mixed with the vegetable oils; the astaxanthin inside the cell was extracted into the vegetable oil phase by hydrophobic interactions, with recovery yields of 88% and above. The oil extracts were simply separated from the culture medium containing cell debris by gravity settling only.

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In order to develop more user‐viable formats for polydiacetylene (PDA) biosensors, it is necessary to control the biochemical and physical properties of the PDA matrix. In this study, we prepare polydiacetylene liposomes from controlled mixtures of 10,12‐pentacosadiynoic acid (PCDA) and PCDA–MI, a PCDA derivative with a maleimide headgroup. Both the chemical and physical properties of the liposome are easily manipulated by controlling the molar ratio of PCDA to PCDA–MI during liposome preparation. After preparing the liposomes, the activity of the maleimide headgroups increases linearly with the PCDA–MI content for concentrations in the range of 0–30 %. As a result, the antibody‐binding characteristics of the PDA liposomes increase with PCDA–MI content. It is also possible to modulate the physical properties of the liposome. Differential scanning calorimetry measurements show that the phase organization of the liposome is progressively lost with increasing PCDA–MI content. Furthermore, the liposomes show an increased color change in response to temperature that is also dependent on PCDA–MI content, indicating increased membrane fluidity. When PCDA:PCDA–MI liposomes are conjugated with a cell‐specific antibody the response to the antigen induces a color change that is dependent on the PCDA–MI content. Consequently, it is deduced that the increased sensitivity of the liposomes containing higher PCDA‐MI content is due to increased antibody binding and membrane fluidity. From these experiments, we identify the factors controlling the colorimetric properties of the PDA matrix and demonstrate that it is possible to modulate the sensitivity and stability of PDA biosensors by controlling the ratio of constituent monomers.