PHAs are usually produced when the microbes are cultured with nutrient-limiting concentrations of nitrogen, phosphorus, sulfur, or oxygen and excess carbon sources. The production of the PHA using oil substrates such as waste oil and plant oil, has gained considerable attention due to the high product yield and lower substrate cost.the substrates can be generally divided into three categories:

1. simple sugars (monosaccharides),

2. triacylglycerol and

3. hydrocarbons.

Most PHA-producing microorganisms can use simple sugars, whilst triacylglycerol have only been reported for some microorganisms. , the use of thermophilic or thermotolerant strains, especially for industrial production of PHAs, offers several cost advantages. Another method to reduce the fermentation cost is the development of production protocols for the bioconversion of inexpensive and renewable carbon (and/or nitrogen) substrates, including waste and by-products from agriculture and industrial sources, instead of pure and refined substrates.20 In fact, recent years have witnessed an increasing trend towards exploration of unconventional substrates for cost efficient production of several types of PHAs

https://www.researchgate.net/publication/282314861_Strategies_for_Large-scale_Production_of_Polyhydroxyalkanoates