Biopolymer: polymers that are made totally or in large part from living organisms (Conquering Chemistry 2)
• Biopolymer PHB(below, right) [poly(3-hydroxybutanoate)] (3 means hydroxy is on third carbon from the carboxylic acid group) à monomer β-hydroxybutanoic acid/ 3-hydroxybutanoic acid (below, left)

1. Culture of microorganisms are fed nutrients under optimal conditions so that it grows and multiplies rapidly
2. When there is enough, "diet" changed, it's limited to one nutrient (e.g. nitrogen) in suitable medium. In this condition it will stop growing and starts to make desired polymer to store as energy source
3. Can produce 30-80% of its own dry weight. Organism harvested and polymer separated out Biodegradable plastics expensive to make compared to petroleum based
Factors determining efficiency of production of PHB
• Rate of production and accumulation of PHB
• Percent of purity and recovery
Alternative microorganisms: E. coli (Escherichia coli)
• Alcaligenes eutrophus genes present in E. coli for reaction to occur
Under same treatment the percent of recovery from E. coli (96%) is higher than A. Eutrophus (80%)which determines cost production.

Alcaligenes Eutrophus (A. Eutrophus)
• It grows efficiently on glucose as a carbon source which is the main nutrient. Glucose is renewable
• Produce about 80% PHB when in sugar rich but nitrogen/phosphate deprived medium

Uses:
• Disposable nappies: it is able to break down faster in the environment thus causing less burden for rubbish dumps (3)
• packaging in the form of bottles, packaging food industry: it is insoluble and stable thus doesn't react to substances