Biofilm reactors for value-added products production: An in-depth review

Biofilms in the environment can both detrimental and beneficial effects. On the other hand, biofilms can be useful for wastewater treatment, bioremediation, and removal of toxic pollutants. Furthermore, biofilms can be used for the productions of value-added products (VAPs) such as biofuels, polysaccharides, antibiotics, organic acids, vitamins, and enzymes. To establish biofilms in the reactors, solid support materials (SSMs) made of inorganic compounds and various agricultural by-products. For these, several types biofilm reactors (BRs) have been utilized such as stirred tank biofilm (bio)reactor (STBR), fluidized-bed biofilm (bio)reactor (FBR), fixed/packed-bed biofilm (bio)reactor (PBR), rotary disc biofilm (bio)reactor (RDR)/rotating biological contactor (RBC), membrane biofilm (bio)reactor (MBR), moving bed biofilm (bio)reactor (MBBR) and trickling filter biofilm (bio)reactor (TBR). The benefits of BRs: increase product yield, provide logarithmic phase growth, reduce lag phase and fermentation time for repeated fermentations, increase biomass population, provide resistance toward toxic compounds, and improve product recovery. This review paper will summarize the literature for biofilm formation and structure, BR types, biofilm support materials, and various VAPs-produced by using BRs.