Zinc bioavailability in young adult rats fed sweet potato greens containing phytic acid.

This study determined whether phytic acid in sweet potato greens influences the bioavailability of zinc in young adult rats used as models for adult humans. A control diet (AIN-93M), two AIN-93M diets with pure phytic acid (PA) at 0.2% or 0.4%, and four diets with Georgia Jet or TU-82-155 dried blanched greens at 7.5% or 15% were fed to seven groups of 7-week male Harlan-Sprague rats for 21 days. Weight gains were generally not affected by PA concentration, were lower in the rats fed with sweet potato greens than in the control rats, and were similar in the rats fed with pure PA or control diet. Feed intake utilization, as indicated by the total weight gain per total feed intake, was almost similar in the different rat groups. Bone (femur, tibia) and organ (kidney, liver, lung, spleen) weights, except the heart weights, were similar for all diet groups. Their zinc concentrations were generally not affected by PA concentration but depended on the PA source.

Biomass yield and composition of sweetpotato grown in a nutrient film technique system.

Sweetpotato cultivar TU-82-155 grown in a nutrient film technique system and separated into foliage, tips, fibrous, string and storage roots at harvest had a total dry biomass of 89.9 g per plant with 38.4% inedible portion. Tips and storage roots, the traditional edible parts, were analyzed for dry matter, protein, fat, ash, minerals (Ca, Fe, K, Mg, Na, Zn), vitamins (carotene, ascorbic acid, thiamin), oxalic and tannic acids, and trypsin and chymotrypsin inhibitors to determine their nutritional quality. Water soluble matter, minerals (Ca, Fe, K, Mg, Na, Zn), cellulose, hemicellulose and lignin concentrations in the edible and inedible parts were obtained to provide information needed for the selection of appropriate bioconversion processes of plant wastes into food or forms suitable for crop production in a controlled biological life support system.

Biological degradation and composition of inedible sweetpotato biomass.

Many challenges are presented by biological degradation in a bioregenerative Controlled Ecological Life Support System (CELSS) as envisioned by the U.S. National Aeronautics and Space Administration (NASA). In the studies conducted with biodegradative microorganism indigenous to sweetpotato fields, it was determined that a particle size of 75 microns and incubation temperature of 30 degrees C were optimal for degradation. The composition of the inedible biomass and characterization of plant nutrient solution indicated the presence of potential energy sources to drive microbial transformations of plant waste. Selected indigenous soil isolates with ligno-cellulolytic or sulfate-reducing ability were utilized in biological studies and demonstrated diversity in ability to reduce sulfate in solution and to utilize alternative carbon sources: a lignin analog--4-hydroxy, 3-methoxy cinnamic acid, cellulose, arabinose, glucose, sucrose, mannitol, galactose, ascorbic acid.