Valorization of shopping center side- and waste streams with plant cell culture technology – Prospects and cost reduction

Upcycling potential of side-streams and waste material, originating from a shopping center were studied as a feedstock for plant cell cultures of arctic bramble (Rubus arcticus L.), barley (Hordeum vulgare L.) and tobacco BY-2 (Nicotiana tabacum L.). Soft drink waste mix, orange peels, expired bread, spent coffee grounds, and brewer's spent grain, were used in cultivation experiments to supplement sucrose in the basic growth medium. Artificial urine was included to represent a future scenario, where also human urine could be used as a circular feedstock along improvement in purification technologies allowing removal of microbes and toxic molecules. Diluted artificial urine was used to replace elemental macronutrients e.g., ammonium, phosphate, and sulphate in the culture medium. Soft drink waste mix and artificial urine contributed to the highest biomass accumulation of the tested side streams. Culture medium composition optimization, exploiting combination of soft drink waste mix and artificial urine, was conducted with design of experiments software. The optimized culture medium contributed to notable culture medium cost reductions of 55 %, 33 % and 45 % for arctic bramble, tobacco BY-2 and barley cell lines, respectively, without compromising the biomass yield. However, modified culture medium induced some changes in the amino acid composition of arctic bramble plant cell biomass, e.g., increased asparagine and decreased arginine, alanine and tyrosine contents. Thus, attention should be paid to the amino acid composition in further studies. Our findings confirm the potential of upcycling side streams and replacing costly growth medium components with so far unutilized resources.