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Assessment of potential of cyanobacterial isolates from Garhwal region for the production of phycobiliproteins

PI— Dr Vidya Dhar Pandey

Cyanobacteria (Blue-green algae), the organisms investigated for the present study, are a morphologically diverse and ubiquitous group of photosynthetic prokaryotes with potential applications in various fields, such as agriculture, aquaculture, nutraceuticals, pharmaceuticals, bioenergy and bioremediation. They produce fluorescent accessory photosynthetic pigments, called phycobiliproteins (PBPs), which are industrially and pharmacologically important natural products. The potential use of phycobiliproteins as non-toxic and non-carcinogenic natural food colorants/additives has been recognised world-wide in view of the toxicity and carcinogenicity of widely used synthetic food colorants/additives. They also find applications in cosmetics and clinical diagnostics. Moreover, they exhibit pharmacologically important activities, such as anticancerous, antioxidative, anti-inflammatory, neuroprotective and hepatoprotective. Because of their rapid growth rate, simple growth requirements, amenability to controlled laboratory culture and ubiquity, cyanobacteria comprise a suitable bioresource for phycobiliproteins. Although cyanobacteria are widely distributed organisms with remarkable ability to grow and survive under varied climatic/environmental conditions, hitherto they represent unexplored or meagerly explored organisms in Uttarakhand.

Cyanobacterial samples were collected from various freshwater (ponds, canals, rivers, rivulets, waterfalls, water channels, puddles etc.) and terrestrial (soils, rocks, walls of buildings/monuments, tree barks etc.) habitats, representing varying altitudes, located in Garhwal region of Uttarakhand. The sampling sites/places from where the cyanobacterial samples were collected include Rishikesh (Dehradun), Doiwala (Dehradun), Dehradun, Kaliyar (Haridwar), Kodiyala (Tehri Garhwal), Neer Garh (Tehri Garhwal), Byasi (Tehri Garhwal), Singtali (Tehri Garhwal), Devprayag (Tehri Garhwal), Narendra Nagar (Tehri Garhwal), Surkanda Devi (Tehri Garhwal), Dhanaulti (Tehri Garhwal), Mulyagaon (Tehri Garhwal), Swargasram (Pauri Garhwal), Pharasu (Pauri Garhwal), Chilla (Pauri Garhwal), Rudraprayag, Augustyamuni (Rudrapryag), Khankra (Rudrapryag), Ukhimath (Rudraprayag), Shiv Nandi (Rudraprayag), Ratura (Rudrapryag), Kund (Rudraprayag), Karanprayag (Chamoli), Gopeshwar (Chamoli), Mandal (Chamoli), Kaleshwar (Chamoli). A total of 21 cyanobacterial species (17 genera), belonging to 6 families (Chroococcaceae, Oscillatoriaceae, Rivulariaceae, Nostocaceae, Scytonemataceae and Stigonemataceae) and 3 orders (Chroococcales, Nostocales and Stigonematales) were isolated from various freshwater and terrestrial habitats located in Garhwal region of Uttarakhand. They include coccoid forms (Synechococcus sp., Synechocystis sp. Aphanothece sp. Aphanocapsa montana, Gloeocapsa sp., and Gloeothece sp.), non-heterocystous simple filamentous forms (Oscillatoria proboscidea, Oscillatoria limosa, Oscillatoria irrigua, Phormidium foveolarum, Phormidium tenue and Lyngbya sp.), heterocystous simple filamentous forms (Rivularia aquatica, Gloeotrichia ghosei, Nostoc


muscorum, Nostoc linckia, Anabaena oryzae sp., Cylindrospermum majus and Calothrix sp.), heterocystous false branched filamentous form (Scytonema sp.) and heterocystous true branched filamentous form (Hapalosiphon sp.) The cyanobacterial species were established as clonal and axenic cultures and grown under suitable growth conditions using BG-11 medium. The growth yield varied with the species, ranging from 1.4 to 2.3 g fresh weight per liter of culture. Specific growth rate of cyanobacterial species varied in the range from 0.06 h-1 for Anabaena oryzae to 0.18 h-1 for Synechococcus sp. In general, the specific growth rate of coccoid (unicellular/colonial) species was observed to be more than that of filamentous species. The laboratory-grown cyanobacterial species were evaluated for the production of phycobiliproteins. The results revealed the presence of all the three types of phycobiliproteins –phycocyanin (PC), allophycocyanin (APC) and phycoerythrin (PE) in varying proportions in the cyanobacteria examined. The total phycobiliprotein content ranged from 4.81% in Synechococcus sp. to 9.33% in Nostoc muscorum on dry weight (d.wt.) basis. In terms of the percent phycobiliprotein of total protein, the lowest (13.17%) and the highest (30.75%) values were recorded in Gloeocapsa sp. and Anabaena oryzae, respectively. PC was found to be the major phycobiliprotein in most of the cyanobacterial species. Quantitatively, PC was followed by allophycocyanin in majority of the species. PE was observed to be the minor phycobiliprotein in cyanobacteria as its level was less than both phycocyanin and allophycocyanin, except in Scytonema sp. Thus, the quantitative estimation of all the three types of phycobiliproteins showed that majority of the species are phycocyanin rich with PC: PE values above 1. The cyanobacterium Scytonema sp. with PC: PE value of 0.70 can be considered as phycoerythrin-rich species. The content of phycobiliproteins varied to a great extent depending on the species, indicating them to be species-specific biochemical features. Factors like temperature, light intensity, photoperiod and pH were found to have profound effects on the content of phycobiliproteins with the optimum values 30°C, 25 µmol photons m-2s-1, 16:08 h/12:12 h and 8, respectively. The results indicate that the phycobiliprotein production in promising cyanobacterial species can be maximized by optimizing the growth/culture conditions. This would be desired to meet the growing demands of phycobiliproteins for the commercial purpose.

Bearing the novelty, the results of the study carried so far are encouraging as they revealed the occurrence of various cyanobacterial species in different habitats/ localities in Garhwal region of Uttarakhand as well as their potential to produce phycobiliproteins. The study is helpful in providing the knowledge of diversity and distribution of cyanobacterial species in the Garhwal region of Uttarakhand for their future application in agriculture (as biofertilizer), pisciculture (as feed), pharmaceuticals, nutraceuticals and environmental bioremediation. The study is important or relevant to the state both academically and socio-economically.


Anabaena

Aphanothece

Calothrix

Chroococcus

Cyanobacterial culture in carboy

Cyanobacterial culture in flasks

Cyanobacterial culture in petriplates

Gloeocapsa

Hapalosiphon

Lyngbya


Nostoc

Oscillatoria

Scytonema

Synechococcus

Synechocystis

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