| As
algae has characteristics of high photosynthetic
efficiency, strong environment adaptability,
short growth cycle and high biological yield,
it is an ideal material to produce biodiesel.
Chlorella is a kind of autotrophic or heterotrophic
green algae whose growth pattern can be changed
by changing chemical composition of its medium.
In the case of heterotrophic growth, high
fat content can be obtained. Heterotrophic
growth not only improves growth efficiency,
but also beneficial to the accumulation of
metabolites (e.g. lipid) in algae cells, reducing
production cost of biomass and lipids.
Coupling
transesterification with heterotrophic growth
is Biodiesel Production from Micro-algae
by Heterotrophic Fermentation.
Micro-algae
provides a novel method to produce oil feedstock
for biodiesel production from heterotrophic
cultivation of micro-alga Chlorella. protothecoids
in bioreactor. It comprises the steps of
screening a specific strain with characteristics
of high yield of biomass and high oil content;
algal-seed-cells cultivating; high-cell-density
fermentation fed with glucose in a large
bioreactor; harvesting algal cells; extracting
oil from dried algal cells; and producing
the biodiesel by reaction of transesterification
using the extracted oil as feedstock.
Couple
of patents and a national invent award have
been approved for this technology.
The results suggest
that heterotrophic fermentation of the specific
strain of C. protochecoides resulted in
great increase of both cell growth rate
(about 10 gL-1d-1) and cell oil content
(about 60%). It provides the feasibility
of industrialization to produce second generation
biodiesel from fermentation algae. The new
pathway of algae fermentation to produce
biodiesel from sugar (or starch, cellulose,
CO2, waste water) not only beats the biodiesel
production from plant oil or animal fat
but also beats the fuel ethanol production
by yeast fermentation.
Now
we are developing a two-step process, i.e.,
algae photosynthetic growth to increase
biomass and then heterotrophic fermentation
to maximize cell density and oil accumulation.
Coupling photosynthesis by using flue gases
with heterotrophic fermentation using hydrolysates
from starch or other carbohydrates enhances
cellular oil content, reduces the house
gases and saves the cost. It addresses biofuel,
environment and economy. Our ultimate goal
is to develop an economically viable and
environmentally friendly industry that uses
micro-algae for biodiesel production.
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