Production of polymers by cyanobacteria grown in wastewater: Current status, challenges and future perspectives

Abstract

Cyanobacteria are prokaryotic oxygenic phototrophs receiving attention in a wide variety of technological applications such as food and feed supplements, and production of valuable polymers. Among these, carbohydrates (e.g. glycogen) and polyhydroxyalkanoates (PHAs) are of increasing interest due to their potential as a biofuel substrate and bioplastics, respectively. However, biofuels and bioplastics from cyanobacteria have seen many years of effort towards commercialization with only limited success. Their main limitation for polymer production is the high cost of the nutrient source; wastewater, as an inexpensive and widely available alternative, may overcome this bottleneck. Though cyanobacteria have demonstrated a capacity to treat wastewater effluents, their cultivation in such a variable environment involves certain challenges of which the chief one is linked to contamination by other species, especially green algae. This would represent a serious drawback during cyanobacterial biomass production and affects further PHA and carbohydrate production. The present study reviews the potential of cyanobacteria to grow in wastewater effluents from different sources. Conditions favoring them in mixed-culture reactors are described, focusing on nutritional and operational aspects. Current advances and future prospects in PHA and carbohydrate production are explored and discussed.

ALBA: A comprehensive growth model to optimize algae-bacteria wastewater treatment in raceway ponds

“…Moreover, some algal species can contain high amounts of lipids, protein or other compounds that become elemental bricks for green chemistry (Chew et al, 2017). Microalgae appear then as new players to recycle nitrogen and phosphorus using the solar energy and providing useful products such as biofuel, bioplastics, or biofertilizer (Uggetti et al, 2014, Arias et al, 2019.…”

Cyanobacterial Polyhydroxyalkanoates: A Sustainable Alternative in Circular Economy

“…Another example of waste being reapplied to the production process, now using microalgae, is the reuse of effluents from the refining of olive oil in the cultivation of microalgae for biodiesel and biopolymers [ 175 ]. This approach can benefit from the implementation and maintenance of an “inter-system ecology”, associating different industries [ 15 , 176 ].…”

“…The dual advantage of production associated with bioremediation has already been described for cyanobacteria and microalgae in general, mainly aimed at the production of biodiesel [ 17 , 188 , 189 , 190 ]. The same concept can be applied to the production of biopolymers by cyanobacteria [ 15 ], naturally transformable organisms, which opens up possibilities for genetic engineering [ 143 , 191 ].…”

“…The use of cyanobacteria as industrial PHA producers makes it possible to reduce the cost of nutritional inputs, since these photosynthetic organisms have fewer nutritional needs than heterotrophic bacteria [ 12 , 13 ]. The potential application of cyanobacteria by-products in industries with high added value [ 14 , 15 ] is interesting from an economic and environmental point of view, even more so if this system is implemented in light of the circular economy ( Figure 1 ).…”

Agro-industrial waste materials and wastewater as growth media for microbial bioflocculants production: a review

“…Depending on various factors (strain, medium composition, operating parameters, etc), the produced microbial flocculants varied in composition (polysaccharides, proteins, nucleic acid, etc) and in the flocculating activity (FA) (Ben Rebah et al 2018). The bioflocculant production can be enhanced through process optimization of various control parameters such culture medium composition (carbon and nitrogen sources, the ratio carbon/nitrogen (C/N), growth factors, mineral salts, etc) and growth conditions (food/microorganism (F/M), pH, temperature, aeration, inoculum rate, etc) (Fang et al 2020, Arias et al 2020, Lv et al 2019, Zhou and Xu (2019, Hu et al 2019. During the investigation of bioflocculant-producing microorganisms, researches started by using synthetic media containing simple sugar (glucose, sucrose, lactose, fructose, maltose, etc), alcohols and organic acid as carbon sources, and yeast extract, peptone, NH 4 Cl, etc, as nitrogen sources.…”