Mycoremediation of Synthetic Dyes: An Insight into the Mechanism, Process Optimization and Reactor Design - Microbial Degradation of Synthetic Dyes in Wastewaters - page 16

low cost nitrogen supplements (urea and ammonium chloride). Further, this resulted
in higher uptake capacity of the fungal biomass (A. lentulus), decreasing the pro-
duction of excess biomass and reducing the production of dye laden waste sludge.

5 Reactor Designs Based on Different Mechanisms

Reactor scale studies are often necessary to evaluate the ef ciency of the developed

technology at industrial scale. Different reactor designs have been proposed by
various researchers, depending upon the principle mechanism involved in the
process of dye removal. The design of the bioreactor for dye removal process
basically depends on two major factors,

rst being the type of organism and its
growth properties i.e. whether it is a unicellular or multicellular microbe; whether it
exhibits mycelial or pelleted growth etc. and second being the mechanism i.e.
biosorption (the microbe need not be provided with nutrient support but contact
between the biosorbent and dye should be maximized), bioaccumulation (nutrient
support is required along with aeration) and biodegradation (nutrient support along
with optimum pH and temperature for maximal enzyme activity needs special
attention). Figure 5 provides a schematic representation of packed bed reactor
(often suitable for dye biosorption) developed for the removal of Violet 14R dye by
the dried and powdered biomass of A. lentulus (Singh 2010 ). The height of biomass
bed can be varied depending upon the contact time required for accomplishing
ef cient dye removal. Second most common reactor design fordye biosorption is

based on the phenomenon of immobilization where the biosorbent is immobilized
on an inert carrier. Gupta ( 2010 ) utilized the blocks of ceramic monoliths for the
immobilization of A. lentulus which were then utilized for the biosorption of Acid
Navy Blue dye (Fig. 6 ).
Fordye removal process requiring the use of living cells, Mishra and Malik
( 2013 ) have proposed the use of three most commonly used reactor designs; con-
tinuous stirred-tank reactor, expanded and packed bed reactors and airlift bioreac-
tors (Fig. 7 ). All these three designs require a constant supply of nutrient and air so
as to keep the cells in their live state. One such design has been demonstrated by
Xin et al. ( 2012b ) where they have utilized air lift column bioreactor to obtain the
pelleted growth of the fungi for removing dye through bioaccumulation mecha-
nism. The air lift bioreactors, promoting pelleted growth of the fungi, have an added
advantage where problems related to biomass clogging are minimized resulting in
higher mass transfer and dye removal. Moreover, pelleted biomass allows quick
separation of dye laden biomass from the treated wastewater.
Reactor designs based on biodegradation process may utilize either the microbial
biomass capable of producing the enzyme responsible for dye removal or the
puri

ed enzyme, such as LiP, laccase etc. The microbial cells may be immobilized
in a suitable bioreactor design for the production of enzyme which then brings
about thedecolorization. For example, Dominguez et al. ( 2001 ) studied degradation
of Poly R-478 dye by three enzymes i.e. MnP, LiP and laccase produced by