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5.3 Industrial Wastewater Importance
Industrial effluents are highly varied from industry to industry and can present a
major pollution threat to the environment if not sufficiently treated. While the production of polyhydroxyalkanoates by microbial mixed cultures treating wastewaters
was first discovered in municipal wastewater plants, in 1974 (Serafim et al. 2008),
many industrial wastewaters may be more suitable due to their typically rich, often
soluble, organic content and limited nutrients, which allows the possibility to exploit
typical polyhydroxyalkanoates accumulation mechanisms (Saharan et al. 2014).
The imbalance of nutrients within industrial waters makes them naturally suitable to
drive organic conversion toward polyhydroxyalkanoates rather than cell biomass
(Valentino et al. 2016). Organics present in industrial wastewater are typically in
high concentration helping to promote high rates of polyhydroxyalkanoates production and may consist of a limited range of organic compounds that can direct selective polyhydroxyalkanoates production.
Many food and agricultural industries produce carbon-rich substrates suitable for
polyhydroxyalkanoates production. The cheese and dairy industry are among the
biggest producers with protein-rich wastes, followed by the potato industry that
produces waste rich with starch (Koller et al. 2017). Olive oil wastewater is an abundant source of carbon-rich feedstocks and is found in many areas around the globe,
especially in the Mediterranean region. Olive mill wastewater was tested as a carbon
source for the production of polyhydroxyalkanoates and accumulated 43% polyhydroxyalkanoates of cell dry weight in a one-step batch (Beccari et al. 2009;
Kourmentza et al. 2009). The wine industry, also, has potential for the production of
polyhydroxyalkanoates. One research group used grape pomace from wine production for the accumulation of polyhydroxyalkanoates. They employed a two-stage
fermenter filled with Pseudomonas putida. The first stage consisted of the sugar
extracted from the pomace for growth, while the second stage relied on a mixture of
octatonic and undecenoic acids for the polyhydroxyalkanoates accumulation phase.
The experiment was conducted in nitrogen-limiting conditions in a fed-batch mode
in a 100 L fermenter. Under these conditions, the wine waste was able to produce a
41.1% of poly(3-hydroxyoctanoate-co-3-hydroxy-10-undecenoate) (Follonier
et al. 2015).
In some cases, the wastewater from industries was tested following a pretreatment step of fermentation in order to convert sugars to fatty acids and increase the
polyhydroxyalkanoates yield (Kourmentza et al. 2017). Wastewater of tomato production was used for polyhydroxyalkanoates production and accumulated 30–39%
of cell dry weight of polyhydroxyalkanoates (Bengtsson et al. 2017). Wastewater
from a milk and ice-cream processing plant produced a polyhydroxyalkanoates content of 42.5% of cell dry weight (Chakravarty et al. 2010), while that from a confectionary bar plant accumulated a higher polyhydroxyalkanoates value of 70–76% of
cell dry weight (Tamis et al. 2014).
S. Sali and H. R. Mackey
5.3 Industrial Wastewater Importance
Industrial effluents are highly varied from industry to industry and can present a
major pollution threat to the environment if not sufficiently treated. While the production of polyhydroxyalkanoates by microbial mixed cultures treating wastewaters
was first discovered in municipal wastewater plants, in 1974 (Serafim et al. 2008),
many industrial wastewaters may be more suitable due to their typically rich, often
soluble, organic content and limited nutrients, which allows the possibility to exploit
typical polyhydroxyalkanoates accumulation mechanisms (Saharan et al. 2014).
The imbalance of nutrients within industrial waters makes them naturally suitable to
drive organic conversion toward polyhydroxyalkanoates rather than cell biomass
(Valentino et al. 2016). Organics present in industrial wastewater are typically in
high concentration helping to promote high rates of polyhydroxyalkanoates production and may consist of a limited range of organic compounds that can direct selective polyhydroxyalkanoates production.
Many food and agricultural industries produce carbon-rich substrates suitable for
polyhydroxyalkanoates production. The cheese and dairy industry are among the
biggest producers with protein-rich wastes, followed by the potato industry that
produces waste rich with starch (Koller et al. 2017). Olive oil wastewater is an abundant source of carbon-rich feedstocks and is found in many areas around the globe,
especially in the Mediterranean region. Olive mill wastewater was tested as a carbon
source for the production of polyhydroxyalkanoates and accumulated 43% polyhydroxyalkanoates of cell dry weight in a one-step batch (Beccari et al. 2009;
Kourmentza et al. 2009). The wine industry, also, has potential for the production of
polyhydroxyalkanoates. One research group used grape pomace from wine production for the accumulation of polyhydroxyalkanoates. They employed a two-stage
fermenter filled with Pseudomonas putida. The first stage consisted of the sugar
extracted from the pomace for growth, while the second stage relied on a mixture of
octatonic and undecenoic acids for the polyhydroxyalkanoates accumulation phase.
The experiment was conducted in nitrogen-limiting conditions in a fed-batch mode
in a 100 L fermenter. Under these conditions, the wine waste was able to produce a
41.1% of poly(3-hydroxyoctanoate-co-3-hydroxy-10-undecenoate) (Follonier
et al. 2015).
In some cases, the wastewater from industries was tested following a pretreatment step of fermentation in order to convert sugars to fatty acids and increase the
polyhydroxyalkanoates yield (Kourmentza et al. 2017). Wastewater of tomato production was used for polyhydroxyalkanoates production and accumulated 30–39%
of cell dry weight of polyhydroxyalkanoates (Bengtsson et al. 2017). Wastewater
from a milk and ice-cream processing plant produced a polyhydroxyalkanoates content of 42.5% of cell dry weight (Chakravarty et al. 2010), while that from a confectionary bar plant accumulated a higher polyhydroxyalkanoates value of 70–76% of
cell dry weight (Tamis et al. 2014).
S. Sali and H. R. Mackey