| In the planned Advanced Life Support System (ALS) for extended duration space exploration missions, hydroponically grown crops will be used to produce food and regenerate oxygen. Typically, a food crop is 40--60% inedible. This material contains fixed carbon and chemical energy representing important resources in the ALS. The carbohydrate portion of the inedible material can be treated and hydrolyzed into simple sugars, and used for a subsequent fermentation to produce valuable products. Therefore, bioconversion of ALS wheat crop residue to simple sugars was investigated and the sugars were used to cultivate Cryptococcus curvatus for single cell oil (SCO) production.; It was found that leaching at 65°C for four hours prior to pretreatment increased saccharification of the crop residue. Alkaline-peroxide pretreatment proved to be more effective than ozonation, with close to 100% saccharification efficiency where ozonation only achieved up to 80% saccharification efficiency. This was attributed to the oxidative, hydrolyzing and swelling effects of alkaline-peroxide treatment compared to only the oxidative treatment from ozone. The conversion of 100 g of wheat straw yielded 35 g of glucose and xylose, These sugars, derived from the hydrolysis of alkaline-peroxide treated wheat straw, successfully supported the growth of C. curvatus producing 13.5 g/L cell weight with 32% of that as lipid. Therefore, 100 g of wheat straw produced 5.5 g of oil. The oil proved to be similar to common edible oils, and most similar to lard in fatty acid composition, melting point, and other physical properties. The fatty add composition of the oil produced by C. curvatus was also modified by changing the aeration rate during cultivation and may be modified with alterations in growth temperature or by mutating the organism.; Additionally, edible oil processing options were evaluated for their potential in the ALS. It was determined that a mechanical process involving extruder seed preparation and expeller oil recovery was most compatible for the ALS when based on consideration of yield, product quality, versatility of equipment, and power requirements. |
