Abstract

Much progress has been made in the cultivation and production of cassava (Manihot esculenta) and cowpea (Vigna unguiculata) in Nigeria. In the present study, investigation was carried out on the possibility of using cassava flour as a source of glucose as well as cowpea as source of nitrogen in the production of yeast. Acid hydrolysis (using dilute H₂SO₄) of cassava and cowpea was undertaken to release the sugars and amino acids. The pH of the growth medium using hydrolyzed cassava as carbon source and cowpea as nitrogen source was varied from pH 2.5 - 6.5. The results obtained show that pH 6.5 gave optimum yeast biomass. The hydrolyzed cassava was also varied in the growth medium. The result obtained shows that increased concentrations of acid-hydrolyzed cassava increased yeast biomass, indicating that hydrolyzed cassava is a good carbon source of glucose for yeast production. It was also observed that yeast biomass using acid hydrolyzed cowpea extract as nitrogen source was high. This is due to the fact that cowpea contains 66.35% of carbohydrate in addition to about 25% protein and hence a good source of carbon and nitrogen in the culture medium. The residual glucose concentration of the yeast culture for each medium was also determined. The result obtained indicates that with increased yeast biomass, there was significant decrease in the residual glucose. Also, there was a significant decrease in pH of the culture media following yeast culture; the culture media tends to be acidic after yeast culture. Therefore, yeast can be produced using acid hydrolyzed cassava flour as carbon source with cowpea as nitrogen source.

Key words: Cassava, cowpea, yeast, acid hydrolysis, glucose, nitrogen source.