ORANGE AND POTATO PEEL EXTRACTS - ANALYSIS AND USE AS BACILLUS SUBSTRATES FOR THE PRODUCTION OF EXTRACELLULAR ENZYMES IN CONTINUOUS-CULTURE

Orange and potato peels were studied in terms of their chemical compos itions and their ability to support the growth and extracellular hydro lytic enzyme production of Bacillus subtilis strain 11089. The orange and potato peel substrates were prepared by blending and removal of la rge particles by filtration. The chemical composition of the filtrates were similar to the crude peel 'starting' material and were shown to contain predominantly alcohol-insoluble solids (pectin, cellulose, sta rch), soluble sugars and minerals (mainly Ca, K, P, and Si). The compo sition of the orange peel (substrate) was different to that of the pot ato peel (substrate) mainly in terms of low levels of starch and prote in, and higher levels of sugars, pectins and cellulose. Bacillus speci es 11089 was capable of growth in continuous culture on both orange an d potato substrates when these were used as the carbon-energy source i n a mineral salts basal medium. Potato filtrate supported the highest growth (mu(max) and biomass yield) but lowest specific activities of o l-amylase, neutral and alkaline proteases, and polygalacturonate-lyase compared to orange filtrate as substrate; however, when enzyme activi ty was expressed as units per volume of culture, potato filtrate suppo rted the highest levels. In all cases, enzyme production using the var ious filtrates alone or mixed (1:1) was similar to or better than that produced by glucose used at the equivalent weight-volume concentratio ns. (C) 1998 Elsevier Science Inc.