Sustainable Applications of Cladophora glomerata Hydrolysates: Nostoc commune Cultivation and Utilizing Biowaste for Agricultural and Environmental Purposes

The green macroalga Cladophora glomerata, a species commonly infesting surface waters, was hydrolyzed by Liquid Hot Water treatment under acidic, neutral, and alkaline conditions. The liquid fraction obtained after hydrolysis was added to BG11 medium to cultivate the valuable cyanobacterium Nostoc commune under mixotrophic conditions, while the insoluble fraction was tested as a biosorbent of metal ions. In addition, cyanobacteria were grown under autotrophic conditions also in the presence of ZnO nanoparticles, biosynthesized using aqueous C. glomerata extract. Mixotrophic conditions with the use of acidic and alkaline algal hydrolysates produced the largest amount of N. commune. The post-culture media after N. commune separation were tested as potential biostimulants of plant growth, while the alga itself and the solid residue after hydrolysis were tested for the biosorption capacity of Cr(III) ions. The study presents an environmentally friendly method to transform the waste algal biomass into beneficial products for agriculture and the environment.