Environmental Engineering Reference
In-Depth Information
Ta b l e 2
M
olecular composition of different
H. pluvialis
populations (% of ash-free dr
y biomass)
Population
Protein
Carbohydrate
Lipid
Green
∗
30.1
35.6
9.3
Reddish
∗
13.8
48.7
18.7
Cysts
∗∗
8.8
51.1
25.5
∗
Green and reddish population generated in continuous one-step system.
∗∗
Cysts generated in two-step batch culture.
the reddish cells generated in the one-step system as compared with that of typical
aplanospores (Table 3). Up to 95% of astaxanthin could be recovered from the red-
dish cells by extraction with methanol/chloroform (1:1), in comparison to a much
lower pigment recovery when applied to cysts. Other chemical or physical treat-
ments rendered always lower recovery from cysts as compared to reddish cells. It
therefore follows that the reddish vegetative cells generated under continuous cul-
ture, lacking a hard cell wall and being amenable to cell disruption and carotenoid
extraction with mild treatments, are an interesting astaxanthin source. The lesser
stiffness of the cell envelopes in the biomass resulting from the continuous produc-
tion process would favor bioavailability of the contained astaxanthin, for example
when cells are used as an additive to fish feed [26, 27, 52]. Moreover, this red-
dish biomass is rich both in astaxanthin and fatty acids, exhibiting high antioxidant
activity, analogous to that of cysts [53].
Thus, the demonstrated capabilities of the one-step production system, as well as
its product quality, made it a viable alternative to the current two-stage systems for
the production of astaxanthin-rich biomass. Performance and efficiency of outdoor
operation needs verification at a convenient time and size scale. In this context, a
recent viability test has been performed outdoors using a pilot scale tubular photo-
bioreactor, consisting of a horizontal loop made of 0.025 m internal diameter tubes
of a total length of 95 m, the culture volume in the reactor being 50 l [44]. The
obtained results clearly support the validity of the developed models for different
Ta b l e 3
Relative fragility of astaxanthin-rich growing cells as compared with aplano
spores
Two- s t ep
aplanospores
∗
astaxanthin recovery
(%)
One-step reddish
cells astaxanthin
recovery (%)
Treatment
Methanol/chloroform (1:1)
94.3
1.7
Methanol 70
◦
C
62.2
24.6
French Press (20,000 psi)
64.2
14.9
Sonication (10 min, 40 W)
48.5
10.1
Astaxanthin was determined as described in Del Río et al. [25] 100% corre-
sponds to 10 and 16 mg astaxanthin per g dry weight, for growing cells and
aplanospores, respectively, disrupted with alumina in a mortar.
∗
Aplanospores generated following nitrate starvation in batch culture.
Search WWH ::
Custom Search