Carbohydrate Biolubricants from Algae and Cyanobacteria

Lubricants are used to prevent friction that causes resistance and heating up in oil drilling; ocular and orthopaedic implant materials; with Metal Working Fluids (MWF) and in general anti-wears. Conventional lubricants are either non-renewable petroleum-based or environmentally unfriendly synthetic materials, while biolubricants are renewable and eco-friendly of 'biological origin'. Biolubricants are derived from either lipids/oils or carbohydrates obtained from living sources like animals (Chitosan, Hyaluronic acid), plants (Gum arabic, Guar gum), algae/cyanobacteria (oil, polysaccharide) and other microorganisms like bacteria (Gellan, Xanthan gum, Dextran, Lichenysin, Surfactin), yeast (single cell oil), filamentous fungi (esters). Lipids/Oils have varied uses in energy (biodiesel), food and other sectors, and are therefore in high demand, while extracellular polysaccharides (EPS) are of limited use at present. Biolubricants from animals have limitations. Similarly, the use of higher plants also has limitations as they require large arable land; only a part of their biomass, not the entire plant useful, and have long-life cycles compared to microorganisms. However, microorganisms like bacteria need specialized equipment and techniques to cultivate, increasing production costs. But, Algae and Cyanobacteria are photoautotrophs with minimal growth requirements and easy to cultivate. The viscous algal/cyanobacterial polysaccharides have remarkable rheological properties useful in reducing friction. Among algae, the seaweed products like agar, carrageenan and alginic acids are shown to provide lubrication, but they are needed more for other uses, and the macroalgae cultivation has its own limitations. Instead, Microalgae and Cyanobacteria pose relatively less problems and produce polysaccharides with remarkable rheological properties and physico-chemical characteristics, fit for lubrication. They can be cultivated round the year, some with seawater or even with wastewater or effluents (resulting also in bioremediation), reducing the cost of biomass production. This review highlights the emerging importance of carbohydrates especially the extracellular polysaccharides (EPS) of Algae and Cyanobacteria with commercial potential as Carbohydrate biolubricants. In addition, algal/cyanobacterial biomass production, together with optimizations required to maximize polysaccharides have been reviewed and the physicochemical properties including molecular weight, crystallinity, thermal characteristic and rheology of polysaccharides useful as biolubricants are discussed.

Automated summary

Biolubricants are renewable and eco-friendly products derived from biological sources like animals, plants, algae, cyanobacteria, and other microorganisms. While animal and plant-based biolubricants have limitations, microorganisms like bacteria, algae, and cyanobacteria offer advantages in terms of easy cultivation, minimal growth requirements, and remarkable rheological properties. The emerging importance of extracellular polysaccharides (EPS) from algae and cyanobacteria as carbohydrate biolubricants with commercial potential is highlighted in this review.