The present invention 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 20 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.

Key Data:

Biomass: 100g( dry weight)/L

Oil: 60%

Fermentation time: 5 days

Technology status: pilot

Material: glucose