Graduate Thesis Or Dissertation
 

Production of Candida utilis from annual ryegrass straw hydrolyzate

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/v979v646m

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  • Post-harvest open field burning of straw has been a common practice of waste disposal and field sanitation for the grass seed industries in the Willamette Valley for over 20 years. This practice has resulted in excessive air pollution. Acceptable new techniques are needed for disposal and or utilization of straw. One possibility would be the industrial production of food and fodder yeast protein from grass straw. Continuous aerobic propagation of yeast on assimilable sugars present in straw hydrolyzates may be a feasible alternative to burning. Milled Annual Ryegrass (Lolium multiflorum) straw (20-40 mesh) was used in this study. The straw was hydrolyzed in an autoclave with 3% sulfuric acid for 30-45 minutes. The hydrolyzate obtained was fortified with NH₄0H as a nitrogen source. The pH was adjusted to 4.0 and the fortification completed with the addition of KC1, H₃PO₄ and magnesium sulfate. After filter sterilization, the fortified hydrolyzate was used as a medium for continuous aerobic propagation of Candida utilis (strain NRRL Y-1084) at 32°C. The effect of sugar concentration and yield constants were studied. The yield constants were found to be in the range of 0.4 to 0.63. Gasliquid chromatographic analysis of sugars in the effluent media indicated that C. utilis preferentially utilized hexose to the pentose sugars. Maximum total sugar utilization was 82%. Arabinose which contributed10 - 15% of the total hydrolyzate sugar was not assimilated. Lyophyilized yeast cells were off-white in color, odorless and contained about 48 - 53% protein on dry weight basis as determined by Kjeldahl nitrogen analysis. Data obtained in this preliminary investigation have shown that Annual Ryegrass straw hydrolyzate can serve as a good medium for Candida utilis production.
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