Cyanobacterial Polyhydroxybutyrate (PHB): Screening, Optimization and Characterization

Abstract

In modern life petroleum-based plastic has become indispensable due to its frequent use as an easily available and a low cost packaging and moulding material. However, its rapidly growing use is causing aquatic and terrestrial pollution. Under these circumstances, research and development for biodegradable plastic (bioplastics) is inevitable. Polyhydroxybutyrate (PHB), a type of microbial polyester that accumulates as a carbon/energy storage material in various microorganisms can be a good alternative. In this study, 23 cyanobacterial strains (15 heterocystous and 8 non-heterocystous) were screened for PHB production. The highest PHB (6.44% w/w of dry cells) was detected in Nostoc muscorum NCCU- 442 and the lowest in Spirulina platensis NCCU-S5 (0.51% w/w of dry cells), whereas no PHB was found in Cylindrospermum sp., Oscillatoria sp. and Plectonema sp. Presence of PHB granules in Nostoc muscorum NCCU- 442 was confirmed microscopically with Sudan black B and Nile red A staining. Pretreatment of biomass with methanol: acetone: water: dimethylformamide [40: 40: 18: 2 (MAD-I)] with 2 h magnetic bar stirring followed by 30 h continuous chloroform soxhlet extraction acted as optimal extraction conditions. Optimized physicochemical conditions viz. 7.5 pH, 30°C temperature, 10:14 h light:dark periods with 0.4% glucose (as additional carbon source), 1.0 gl-1 sodium chloride and phosphorus deficiency yielded 26.37% PHB on 7th day instead of 21st day. Using FTIR, 1H NMR and GC-MS, extracted polymer was identified as PHB. Thermal properties (melting temperature, decomposition temperatures etc.) of the extracted polymer were determined by TGA and DSC. Further, the polymer showed good tensile strength and young’s modulus with a low extension to break ratio comparable to petrochemical plastic. Biodegradability potential tested as weight loss percentage showed efficient degradation (24.58%) of PHB within 60 days by mixed microbial culture in comparison to petrochemical plastic.

Advanced biofilm staining techniques for TEM and SEM in geomicrobiology: Implications for visualizing EPS architecture, mineral nucleation, and microfossil generation

“…7A,B). These hydrophobic storage molecules are typically 200-500 nm in size (Reusch, 2012), can account for up to ~6% dry weight of cells (Ansari and Fatma, 2016), and are known to bind calcium, as indicated by EDS analysis in the present study (Fig. 7B, overlain) (Reusch and Sadoff, 1988).…”

Cyanobacterial Polyhydroxyalkanoates: A Sustainable Alternative in Circular Economy

“…In addition to application in segments with high added-value, such as the pharmaceutical market [ 132 ], the possibility of producing cyanobacterial biomass at a reduced cost allows its application in mass industries, which, as a rule, demand cheap production and on a large scale, such as the food and agriculture industry, with the use of cyanobacteria biomass and pigments as food and animal feed [ 133 , 134 ].…”

“…In addition to pigments, S. salina biomass has carbohydrates, lipids and proteins [ 181 ], which can be used for animal feed [ 134 ], provided that the necessary nutritional requirements and laws regarding the presence of contaminants such as heavy metals or mycotoxins are observed [ 182 ], and in this case, cyanotoxins [ 183 ], giving priority to non-toxin-producing cyanobacteria. The residual biomass of cyanobacteria would therefore be well-used in the nutrition of livestock and aquaculture, but it is possible to go further in the optimization of this production chain.…”

“…Still, using Spirulina sp. as an example, its supplementation to animal feed has already been studied in shrimp, fish and chicken farming [ 134 , 185 ], valuing the production of this associated industry, improving the growth and coloring of tilapia [ 186 ] and egg yolks of chickens fed with S. platensis astaxanthin [ 187 ]. Animal health is also benefited by nutritional supplementation with cyanobacteria, with Spirulina sp.…”

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“…It is riched source of protein, carbohydrates, lipids and other pigments. They possesses vital role in neutraceuticals and pharmaceuticals and is very vast and thrusting area of research [2][3][4][5][6][7][8][9] .…”