Passively immobilized cyanobacteria Nostoc species BB 92.2 in a moving bed photobioreactor (MBPBR): Design, cultivation, and characterization

Abstract

The cyanobacterium Nostoc sp. BB 92.3. had shown antibacterial activity. A cultivation as biofilm, a self-forming matrix of cells and extracellular polymeric substances, increased the antibacterial effect. A new photobioreactor system was developed that allows a surface-associated cultivation of Nostoc sp. as biofilm. Highdensity polyethylene carriers operated as a moving bed were selected as surface for biomass immobilization. This system, well established in heterotrophic wastewater treatment, was for the first time used for phototrophic biofilms. The aim was a cultivation on a large scale without inhibiting growth while maximizing immobilization. Cultivation in a small photobioreactor (1.5 L) with different volumetric filling degrees of carriers (13.4%-53.8%) in a batch process achieved immobilization rates of 70%-85% and growth was similar to a no-carrier-control. In a larger photobioreactor (65 L) essentially all of the biomass was immobilized on the carriers and the space-time yield of biomass (0.018 g cell dry weight L −1 day −1 ) was competitive compared to phototrophic biofilm cultivations from literature. The use of carriers increased the gas exchange in the reactor by a factor of 2.5-3 but doubled the mixing time. Enriched gassing with carbon dioxide resulted in a shortterm increase in growth rate, but unexpectedly it also adversely changed the growth morphology.

Unveiling the Cultivation of Nostoc sp. under Controlled Laboratory Conditions

“…Since Nostoc is recognised for its environmental and biotechnological applications, over the past decades, research has been geared towards finding the optimum conditions for its production in aquaculture. Studies on nutrient supply [19,20], photoautotrophic, mixotrophic, and heterotrophic cultivation [21], light intensity and quality [22], and the type of bioreactor used [23][24][25], among others, have produced valuable knowledge on the cultivation of different Nostoc species. Other authors have focused on the production of bioactive compounds, namely the exopolysaccharides [26][27][28], phycobiliproteins [29,30], cyanophycin [16], polysaccharides [31], and biodegradable polymers [32,33], as well as mycosporine-like amino acids [34].…”

Cultivation of Cyanobacteria on Sustainable Dried Luffa cylindrica

“…To maintain this aspect of sustainability, the carriers used for the cultivation of biofilm-forming cyanobacteria in submerged systems should also be biodegradable and thus sustainable. So far, various materials have been successfully used as carriers for immobilized cultivation of cyanobacteria such as fibers and fabrics [10,11], open-cell foams such as polyurethane (PUR) [12,13], or high-density polyethylene (HDPE) [14]. Plastics are always problematic if a product is to be produced sustainably.…”

Cultivation of Cyanobacteria on Sustainable Dried Luffa cylindrica

“…To maintain this aspect of sustainability, the carriers used for the cultivation of biofilm-forming cyanobacteria in submerged systems should also be biodegradable and thus sustainable. So far, various materials have been successfully used as carriers for immobilized cultivation of cyanobacteria such as fibers and fabrics [14,15], open-cell foams such as polyurethane (PUR) [16,17], or high-density polyethylene (HDPE) [18]. Plastics are always problematic if a product is to be produced sustainably.…”