Optimizing the Continuous Production of Candida utilis and Saccharomycopsis fibuliger on Potato Processing Wastewater

Abstract

The yeasts Candida utilis and Saccharomycopsis fibuliger were propagated as a source of single-cell protein in a continuous, mixed, aerobic, single-stage cultivation on blancher water generated during potato processing. A series of steadystate experiments based on a two-level factorial design, half-replicate modified with an intermediate experiment, was performed to determine the effect of pH, 3.8 to 4.8; dissolved oxygen, 42 to 80% saturation; dilution rate, 0.17 to 0.31 h-1I and temperature, 27 to 320C on the amount of carbon consumed, the rate of carbon consumption (Rc), the amount of reducing sugar consumed, the rate of sugar consumption (Rg), the amount of protein produced, the rate of protein production (Rp), the yield from carbon, and the yield from reducing sugar. The results were analyzed by stepwise multiple regression and Fisher's least significant difference test. Analyses showed that high dilution rates resulted in increased Rc, Rg, and Rp and indicated that a rate of 0.31 h-1 was below the critical dilution rate. A temperature of 320C increased the amount of carbon consumed by 34%. A pH of 4.3 to 4.8 increased the amount of protein produced. The yield from carbon was constant, and the relatively high yield from reducing sugar indicated that other substrates were consumed. Dissolved oxygen was in excess at 42% saturation and above. Since C. utilis predominated the mixed cultures and amylase production appeared to be limited, a single-stage fermentation lacked efficiency. The experimental design allowed preliminary optimization of major environmental variables with relatively few experiments and provided a basis for future kinetic studies.

Investigation of Cashew Apple Juice as a Substrate for Single Cell Protein Production

“…The nuts, which have hitherto been the primary products of interest, are separated from the apples which are generally wasted. Such wastes may be used in microbial processes (Lemmel et al, 1979;Moreton, 1978;Bloch et al, 1973;Jarl, 1969;Solomon et al, 1981;Layokun, 1984).…”

The Use of Selected Strains of Yeasts in the Treatment of Processing Wastewater From Lye-Peeled and Steam-Peeled Potatoes

“…In the wastewater inoculated with the mixture of C. utilis and S. fibuliger, a slightly better CODreduction was achieved during the 72 h incubation period, compared to the wastewater treated with C. utilis. This is possible because S. fibuliger produces amylases that break down the starch in potato wastewater to glucose, followed by the consumption of the breakdown products as well as sugars already present in the wastewater by both S. fibuliger and C. utilis (Lemmel et al 1979).…”

“…However, a symbiotic relationship of these organisms may reach a stage whereby the Candida removes the glucose at a faster rate t h a n the S. fibuliger can hydrolyze starch, thereby suppressing the growth of S. fibuliger, which would then release insufficient glucose from the starch of wastewater for optimum growth of both organisms. Thus, as suggested by many researchers (Jar1 1969; Moreton 1978;Lemmel et al 1979) it would be best to grow C. utilis and S. fibuliger separately on potato processing wastewater, whereby S. fibuliger could be grown in the first stage to produce amylases and the mixed culture in the second stage to produce single-cell protein. Preliminary experiments were conducted in which S. fibuliger was grown first to break down the starch, followed by treatment with other yeasts to produce protein.…”

“…In recent years, efforts have been made to treat food processing wastewater with yeasts. Lemmel et al (1979) and Skogman (1976) have reported that the strength, or Biochemical Chemical Oxygen Demand (BOD), of potato processing wastewatercan be reduced as much as 90% by using a yeast controlled fermentation step before treatment, in which a valuable by-product (single-cell protein) is formed. The "symba yeast process" developed by a Swedish sugar company is well-known for its success in treating potato processing effluent by using a symbiotic culture of the yeasts Endomycopsis fibuliger (E. fibuliger) and Candida utilis (C. utilis) (Skogman 1976).…”

Protein production by Schwanniomyces castellii on starchy substrates, in liquid and solid cultivation

“…Many processes have been described for converting different forms of starchy substrates into single cell protein (SCP). First studies on biomass production from starch agricultural or industrial wastes and waste waters involved a preliminary hydrolysis stage of the substrate by chemical (Tong, Riel & Simard, 1973), enzymic (Schierbaum, Richter & Nordheim, 1968;Moreton, 1978;MusCnge, Anderson & Holdom, 1982) or microbial means (Jarl, 1969;Lemmel, Heimsch & Edwards, 1979).…”