Bio

mas

s or

Oil

(g/L

)

0

10

20

30BiomassSCOECO

Bio

mas

s or

Oil

(g/L

)

0

10

20

30

40

50 BiomassSCOECO

Lucas McNea & Robert W. NicolUniversity of Guelph – Ridgetown Campus, Ridgetown ON Canada N0P 2C0

Centre for Agricultural Renewable Energy and Sustainability, www.ridgetownc.com/cares

BIOCONVERSION OF BIOFUEL CO-PRODUCTS TO SINGLE CELL OIL

ABSTRACTThin stillage and crude glycerol are produced during manufacture of ethanol and biodiesel respectively. Although there is some demand for these biofuel co-products, their full value has not been realized due to a saturated distillers grains market and due to the low purity of crude glycerol. Our goal is to use these substrates in a novel bioconversion application based on the newly described oleaginous fungus Galactomyces geotrichum. Thin stillage was found to have a pH of 4.8 and potential fungal inhibitors, organic acids and residual ethanol, were found to be low at 0.3%. Crude glycerol was found to have a pH of 9.4 and be composed of 29.7% residual oils, 28% glycerol and 26% methanol. Quantity of elements was generally low except for potassium, originally from the potassium hydroxide catalyst, which was found at a concentration of 28,000 µg g-1. Galactomyces geotrichum was cultured in a range of biofuel co-product concentrations and found to produce 12.5 to 41.0 g L-1 biomass, and 2.1 to 50.1 g/L of oil. Galactomyces geotrichum is a promising microorganism for valorizing biofuel co-products and work on scaling-up this process will continue.

Corn

ThinStillage*

Stillage EtOH

CDS

WDG

CrudeGlycerol*

Bio-diesel

Vegetable Oil

Figure 1: Simplified ethanol production process. Thin stillage is the mostly liquid fraction of the whole stillage and was used in this study.

Figure 4: Biomass and oil production by Galactomyces geotrichum cultivated for 5 (A) or 3 (B) days in mixtures of biofuel co-products. There is 29 g/L of residual oil in the co-products, so total oil above this level, as seen in CG + 100% TS, represents a net gain. TS=thin stillage, CG=50 g/L crude glycerol, SCO=single cell oil, ECO=extracellular oil (recovered from spent medium).

Figure 3: Bioconversion of mixtures of thin stillage from ethanol production and crude glycerol from biodiesel production. Galactomyces geotrichum converts these biofuel co-products to single cell oil, a new biodiesel feedstock or potentially useful in higher value applications.

Figure 2: Simplified biodiesel production process. Crude glycerol is a product of the transesterification of the triacylglycerol molecule and was used in this study.

distillation

centrifugation

+evaporation

+

DDGS

MeOHKOH

ThinStillage

CrudeGlycerol

Bioconversion

SingleCellOil

100% TS

70% TS

CG + 10% TS

CG + 70% TS

CG + 100%

TS

100% TS

CG + 70% TS

A B

Fatty acid Amount (%)

16:0 12.5116:1 0.8918:0 3.8718:1 35.4618:2 37.3918:3 3.3520:0 0.3720:1 0.44

Table 1: Fatty acid composition of the single cell oil by GC-FID.

SUMMARY•Galactomyces geotrichum was able to grow in untreated thin stillage and crude glycerol

•this fungus readily produced biomass, but only produced a net gain of oil in undiluted thin stillage plus 50 g/L crude glycerol

•the single cell oil contains very little omega-3 fatty acids, but is suitable for biodiesel production