Environmental Engineering Reference
In-Depth Information
Lin
et al.
demonstrated the potential of bakery wastes (pastries and cakes) as a
valuable source of (bio)succinic acid
3,
a useful platform molecule or biodegrad-
able polymers (e.g. polyhydroxybutyrate
4
), through judicious selection of micro-
bial strains in fermentation processes [81, 82].
O
CH
3
O
HO
OH
H
O
OH
n
O
3
4
Fermentation of sugary wastes is a classical route to C
2
(bio)ethanol, but Atsumi
et al.
[83] have developed non-fermentative pathways for synthesis of branched-
chain higher alcohols as biofuels using bio-engineered strains of
Escherichia coli
to successfully produce C
4
bioalcohols (butanol and isobutanol). Waste coffee
grounds have been successfully exploited as a source of fatty acids and fatty
acid esters suitable for conversion into biodiesel. Waste coffee grounds are rich
in oils (10-15% by weight dry basis) with a profile amenable for conversion to
biodiesel; this is very interesting as coffee is the second most-traded commodity
in the world [84].
Proteins from food waste are an essential source of amino acids that can be
converted into bulk organic chemicals. For example, l-phenylalanine
5
can be
converted to styrene
7
via cinnamic acid
6.
Interestingly, the fermentative produc-
tion of l-phenyalanine
5
from biomass has become so efficient that the most
economical way to produce cinnamic acid
6
is probably from l-phenylalanine
5
by the reverse reaction [74].
CO
2
H
CO
2
H
PA L
NH
2
5
6
7
PA L=L-phenylalanine ammonia lyase
Glutamic acid
8
and lysine
9
can be hydrolysed from proteinaceous food
wastes and serve as a potentially useful feedstock chemical for a variety of
commodity chemicals. For example,
N
-methylpyrrolidone (NMP)
10
and
N
-vinylpyrrolidone (NVP)
11
can be sourced from glutamic acid
8,
whereas
lysine
9
is a source of 5-aminovaleric acid
12,
1,5-diaminopentane
13
and
caprolactam
14
[74].
