###### Abstract  
The bioactive compounds produced by actinobacteria have played a major role in antimicrobials, bioremediation, biofuels, enzymes, and anti-cancer activities. Biodegradable microbial flocculants have been produced by bacteria, algae, and fungi. Microbial biofloculants have also attracted biotechnology importance over chemical flocculants as a result of degradability and environmentally friendly attributes they possess. Though, freshwater actinobacteria flocculants have been explored in biofoculation. Yet, there is a paucity of information on the application of actinobacteria flocculants isolated from the marine environment. Similarly, marine habitats that supported the biodiversity of actinobacteria strains in the field of biotechnology have been underexplored in biofoculation. Hence, this review reiterates the need to optimize culture conditions and other parameters that affect biofoculant production by using a response surface model or artificial neural network.  
marine environment; actinobacteria; flocculating activity; biofloculants; application +
Footnote †: journal: Applied Sciences  
1  
M. A.  
the treatment of different wastewaters, removal of steroid estrogen, precipitation of pharmaceutical proteins, adsorption of heavy metals, drinking water purification, food processing, and fermentation industries [9; 10]. On the other hand, inorganic flocculants (polyaluminum chloride and ferric chloride) and organic flocculants (polyacrylamide amide and polyethylenimine) are also used in wastewater treatment and other biotechnological applications. However, their applications pose a threat to aquatic organisms and human beings [11]. For instance, applications of chemically synthesized compounds have been associated with various health diseases concerns including Alzheimer's, genotoxic disorders, and carcinogenicity. Another important factor is the cost of chemical flocculants which are not affordable for many developing countries. The setbacks attributed with chemical flocculants have necessitated the exploration of biodegradable flocculants which are environmentally friendly and can be used to replace the biotechnological applications of the synthesized flocculants. Biodegradable flocculants produced by microorganisms including actinomycetes are currently gaining traction due to their advantage of environmental friendliness. Some of these biofoculant-producing microorganisms have been isolated from sludge, soil, wastewaters, rivers, dams, alkaline lake, and marine intertidal sludge [12; 13]. Actinobacteria strains isolated from freshwater, dams, and sludge have been implicated in biofoculation and their industrial applications in wastewaters treatment have been validated. However, there is paucity of information regarding marine actinobacteria biofoculant and their role in flocculation. Hence, there is need to explore the diversity of marine actinobacteria for biofoculation and validate their possible industrial applications in dye and heavy metals removal, wastewater treatment, and synthesis of nanoparticles. On this note, this review summarizes actinobacteria that have been isolated and screened from the freshwater environment and the need to explore marine actinobacteria biofoculant and validate their potentials in biotechnology.  
Flocculants can be classified into organic, inorganic and natural flocculants as itemized in Table 1 below.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Inorganic Flocculants** & **Organic Flocculants** & **Natural Flocculants** \\ \hline Polyaluminum chloride & Polyacrylamide & Chitosan \\ \hline Aluminum sulphate & Polyethylene amine & Cellulose \\ \hline Aluminum chloride & & Gum and mucilage \\ \hline Ferric chloride & & Sodium alginate \\ \hline Alum & & Tannin \\ \hline Ferrous sulphate & & Microbial flocculants \\ \hline \hline \end{tabular}
\end{table}
Table 1: Classes of flocculants.  
Figure 1: Diagrammatic description of the biofoculation process (created with BioRender.com).