• 作者： 邱健人
• 作者服務機構： 國立中興大學
• 中文摘要： We have searched for low-cost carbonmaterials for the production of single cellprotein, and have succeeded in getting a highyield of cell mass from acetate and n-paraffin.During the study on methanol as substratefor microbial growth, we found several yeaststrains growing well in methanol medium. These yeasts were isolated from the sam-ples of fruits, vegetables and soil in Taiwanby using the enrichment techniques. From shake flasks inoculated with 1 gmof sample and held at 38°C for 4-5 days, 10strains of yeast that could utilize methanolwere obtained. After 3 times of subculturalpure isolation, three strains of yeast showedgood growth in the methanol medium andwere selected for further study. In order to find cheaper organic nutrientsto be used as growth factor, several organicnutrients such as molasses, rice bran andwheat bran were added at various concentra-tions to the basal medium for examination. First, various concentrations of molassesfrom 0 to 0.75% were tested as growth factorsfor cell growth. The growth of cells incre-ased with the concentration of molasses evenas high as 0.75%, but 0.5% was the optimalconcentration of molasses. Secondly, the addition of various amountsof wheat bran or rice bran to the culturalmedium also promoted the cell growth justlike molasses. On the basis of these results,it can be concluded that only the additionof 0.5% molasses, wheat bran or rice branas growth factor a maximum growth inmethanol medium for these strains of yeastcould obtained. The other organic sources were also exa-mined for their effects on cell growth ofthese strains. Each organic nitrogen sourcewas added to the basal medium containingmineral salts and 2% methanol. Yeast ex-tract as compared to other organic nitrogensources tested appears to be a best growthfactor for production of cells. Malt extractand casein hydrolyte were next best, andvitamin complexes and nucleic acid hydrolytedid not show any effect on the growth ofcells. The growth of methanol utilizing yeastson methanol medium was known to requireseveral kinds of vitamins as growth factors.The effects of vitamins on cell growth ofthese strains were examined by substitutingthe natural nutrient for the basal medium.None was as effective as the basal mediumcontaining natural nutrient. However, thia-mine HCl, biotin and vitamin showedslight stimulation on the growth of theseyeasts. When various concentrations of phosphatewere addes to methanol medium, the growthof cells increased with the increase of con-centration from 0.1% to 0.3% of or But when it exceeded to 0.4%, theincrease of cell growth was not noticeable, In a series of runs with various initialpH concentrations, it was found that thestrains of yeast A-23 could grow equally wellover the broad pH range of 2.5-9.0, butthe maximum growth was obtained whenthe pH of the medium was adjusted to pH3.5 by ammonia water. Above or belowthis pH showed decrease of the growth. It was well known that the factor limit-ing the productivity of a fermentor inhydrocarbon fementation is the ability oftransferring oxygen to growing culture. Inthese studies also indicated that a high aero-bic condition was necessary for a good growthof this strain. The optimal aeration was 1:2vvm at 750 rpm agitation speed. A typical course of fermentation withA-23 strain is shown in Fig. 12. The cellgrowth increased exponentially after 24 hrs,thereafter it increased almost linearly up to58 hrs and reached the stationary phase at60 hrs. In this experiment, maximum cellconcentration was up to 3.65% and the yieldwas 39.2%. Taxonomical characteristics of these iso-lates are examining, but the results are notcompoetely identified.
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