Page 77 - Refining Biomass Residues for Sustainable Energy and Bioproducts

52 Refining Biomass Residues for Sustainable Energy and Bioproducts

2. Polysaccharides: A polymeric carbohydrate comprising long chains of monosaccharide
(sugar molecules); for example, cellulose, hemicellulose, extracellular polymeric sub-
stances (EPS).
3. Polyamides: A macromolecule with a number of amide linkages in between; for example,
wool, cyanophycin.
4. Inorganic polyanhydrides: A biopolymer whose backbone chain is connected with anhy-
dride linkages; for example, Gliade and polyphosphates (Domb et al., 1994).
The main factor behind the production of such polymers is the substrate used
during the formation. A cost-effective production is a necessity to promote the sus-
tainable approach. Waste substrates, such as oil mill waste, food waste, glycerol,
scrap metals, sludge, potato starch waste, and microbial biomass, will help in shap-
ing the process to a feasible end (Morillo et al., 2006). The usage of waste in biopo-
lymers will provide two-way benefits, removing the increasing waste as well as
generating useful materials in a cost-effective manner (Fig. 3.1). Many of these
polymers behave similarly for most of the bacterial domain while sometimes a few
of these can have specific properties with regard to a certain species (Rehm and
Valla, 1997). There are uncountable functions served by biopolymers, such as drug
delivery, protective structure, and storage moieties. When they are exposed to the
ecological setup, they get easily break down to CO 2 and H 2 O by the hydrolytic and
depolymeric microbial attack making them biocompatible (Rehm, 2010). One more
concern that needs to be addressed is to carefully judge the ecological performance
of the produced polymers. This is achieved by LCA (life-cycle assessment), which
provides a comprehensive and solid information about a process (Narodoslawsky
et al., 2015). It is a cradle-to-grave approach which judges the feasibility and the
associated environmental impacts. LCA for production of biological polymers will
help in optimizing these processes making them feasible and approachable for com-
mercial production and applications.
For the present chapter, our focus would be on two significantly contributing
biopolymers: EPS and PHAs. Both of these polymers are cosmopolitan to the
microbial world while the production amount varies from one another. The avail-
able literature surveys for both of these are widely dispersed while the application
prospective can still be better discussed.

3.2 Fundamentals of biopolymers

3.2.1 Polyhydroxyalkanoate
PHA is one of those biopolymers, which is attracting a lot of attention nowadays as
it shows analogical similarity to green plastic. Today’s scenario evidently presents
the distorted picture of our ecosystem created due to the plastic menace. The esti-
mates reveal that every year, more than 120 million tons of plastic is produced out
of which 40% 50% finds its way to landfill. A significant section is dumped into
the marine bodies. Plastic enters our ecosystem through various paths and hampers
not only our environment but also the surviving organisms within. This needs an