Biotechnology for Zero Waste – Emerging Waste Management Techniques (Chaudhery Mustansar Hussain (editor) etc.)

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

Organic waste

(food waste/dairy and milk waste/starch waste/sugar waste/wastewater)

Pretreatment

Anaerobic/aerobic

digestion

Microbial action

Bioenergy

CO2

Ethanol

Methane

Other

PHA

PHB

Polymer

Biodegradable plastics

Fermentation with microbial action

at specific pH, temperature, and time.

Figure 2.1

Schematic representation of deriving biodegradable plastics and bioenergy

from waste materials.

anaerobic digestion (AD) of food waste and biogas can be subsequently used for the

production of electricity or thermal energy (http://www.eesi.org/papers/view/fact-

sheet-biogasconverting-waste-to-energy) [4].

2.2.1

Biodegradable Plastics from Food Waste

Food wastes are rich sources of oil, fat, mineral, protein, carbohydrates, and other

components. Food waste can be converted into value-added products like PHAs,

alcohols, gases, organic acids, etc., by fermentation and conditions like microbial

composition, pretreatment, temperature, pH, humidity, oxygen levels, etc., need to

be optimized for the efficient production of products from waste. For the commercial

production of PHA from different kinds of sources, few bacteria were identified out

of 250 natural producers of PHA. The Pseudomonas oleovorans, Bacillus megaterium,

Alcaligenes latus, and Cupriavidus necator are the microbial strains most widely uti-

lized for the production of PHA [5]. The food waste containing cellulose, fat, fatty

acid, protein, and starch was used as substrate for growing bacteria, Halomonas cam-

paniensis LS21 and Halomonas hydrothermalis, and approximately 70% of PHB pro-

duction was observed at pH 10 and 37 ^∘C. The PHB yield of 0.1 g/g of dairy waste was

observed by the action of B. megaterium SRKP-3 strain [4]. An activated sludge can be

used as source of microbes while fermenting food waste for the production of PHA.

In contrast to the pure culture, the use of activated sludge as mixed culture removes

the necessity for the aseptic conditions, which intern reduces the operating cost [6].