Biosynthesis of Polyhydroxyalkanoates using Starch

Starch is a renewable carbon source abundantly available from plant sources. However, it is usually hydrolysed to glucose via a two-step process, liquefaction and saccharification, before adding it into the polymer prodnction medium [26]. Kim [27] reported P(3HB) production from starch using Azotobacter chroococcum via a fed-batch fermentation. A PHA content of 46 and 20 wt% with a CDW of 54 g/1 and 71 g/1 were obtained with and without oxygen limitation, respectively. A halophilic bacterinm, Haloferax mediterrane was also reported to be able to produce P(3HB) from starch, but the strain was not favourable due to the salt required for its growth which contributed significantly to the PHA manufacturing cost. 

The application of whey, a main by-product in the manufacturing of dairy products and cheese, has been widely explored in the production of PHA. Whey serves as an excellent carbon and energy source as lactose makes up 70% of the total dry matter. Whey retentate is mainly composed of a-lactalbumin and P-lactoglobulin proteins which can be employed as a nitrogen source for the enhanced cultivation of microbial PHA-producing strains [2, 34, 35]. However, the inability of some PHA-producing strains to utilise raw whey has 

Two bacterial strains. Pseudomonas oleovorans NRRL B-14682 and Pseudomonas corrugata 388 were employed to convert the co-product stream resulting from soy-based biodiesel production (CSBP), which contained glycerol, FFA soaps and residual fatty acid methyl esters 

According to Mothes and co-workers [43], the crude glycerol samples obtained from different production plants varied in their composition, 

Javers and co-workers [49] considered soapstock, the co-product of biodiesel production, as a carbon and energy source in the biosynthesis of PHA using a fed-batch feeding strategy and Pseudomonas putida 

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