24

2 Integrated Approaches for the Production of Biodegradable Plastics and Bioenergy from Waste

in 24 hours of cultivation time, with improved productivity of PHB (1.27 g/l/h). The

system was suboptimal due to limiting dissolved oxygen and capable of further

improvements for PHB production rate [16, 20].

2.4.1.2

Bioenergy from Sugar Waste

Alcoholic fermentation of sugar waste will lead to ethanol fuel production [21].

The general chemical equation for the alcoholic fermentation is

C6H12O6 →2C2H5OH + 2CO2

Step-by-step process has been given in Figure 2.2.

2.4.2

Starch Waste

Starch waste can be obtained from cassava, corn, and other cereal crop residues.

The mixed culture of Clostridium butyricum and Enterobacter aerogenes could pro-

duce hydrogen from starch at a yield of about 2 mol-H2/mol glucose, and hydrogen

production of about 6 mol-H2/mol glucose could be obtained from the starch using

a mixed culture of C. butyricum and Rhodobacter sp. M-19 [22, 23].

Fructose (C6H12O6)

Glucose (C6H12O6)

Sucrose (C12H22O11)

H2O invertase

2NAD†

2NAD†

2NADH

2NADH

ethanol

2H2O

Glycolysis

2ADP

2ATP

CO2

Pyruvate

decarboxylase

Alcohol

dehydrogenase

2CH3COCOOH

2CH3CHO

2C2H5OH

acetaldehyde

pyruvic acid

Figure 2.2

Pathway that leads to ethanol from sucrose.