UTILIZATION OF POTATO PULP FROM POTATO STARCH PROCESSING

Potato pulp consisting of pectins, starch, cellulose and hemicellulose was separated by treatment with dilute sulphuric acid into pectins and starch on the one hand and cellulose and hemicellulose on the other. Pectins and starch were separated by fractional precipitation with methanol or acetone. The pulp residue (PR) consisting of hemicellulose and cellulose was enzymatically converted to glucose and xylose and fermented by Pachysolen tannophilus to produce ethanol. The PR and the residue of the enzymatic decomposition (RES) were used as substrates for enzyme production by Trichoderma reesei Rut C30 and Trichoderma reesei MGC 77 in batch and continuous cultures. The highest specific enzyme activities (6.1 U mg-1 avicelase, 23.4 U mg-1 CMC-ase and 66.8 U mg-1 xylanase) and productivities (8.9 U litre-1 h-1 avicelase, 34.3 U litre-1 h-1 CMC-ase and 97.8 U litre-1 h- 1 xylanase) were obtained with RES in batch cultures. The enzyme mixture in the cultivation medium was concentrated by UF membrane treatment and diafiltration. The product quality was comparable with commercially available cellulases. The economy of the upgrading process is mainly influenced by the utilization of pectins, starch, and enzymes. Ethanol production from the hydrolysate of cellulose/hemicellulose is not economic because of the low sugar concentration in the hydrolysate.