Microbial Production of Potent Phenolic-Antioxidants Through Solid State Fermentation - Sustainable Biotechnology: Sources of Renewable Energy - page 236

Fig. 5 Chemical structure of
ellagic acid
production. Also, a biodegradation process of ET's for EA production has been
proposed [73]. SSF is one of the most attractive alternatives to management of agro
industrial by-products, in this case the residues of pomegranate husk contain an
interesting profile of nutrients such as large amounts of insoluble carbohydrates,
small amount of protein, minerals and some remaining juice and other soluble sub-
stances favoring a rapid microbial growth. These properties can be approached for
the production of high value-added metabolites. Figure 5 depicts a typical structure
of ellagic acid .
Extraction of bioactive compounds from plants is conventionally performed
by heat-reflux extraction method. Nevertheless, different techniques including
ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid
extraction, and accelerated solvent extraction have been developed in order to
decrease the bioactive compounds extraction time, as well as the solvent con-
sumption, increase the extraction yield, and enhance the extracts quality [84-86].
Antioxidant phenolics extraction from Larrea tridentata is usually performed by
conventional extraction by reflux. However, further research is needed in order to
maximize the antioxidant's extraction lowering time and energy costs.
3 Technical Details
Figure 6 presents a scheme of work when phenolic antioxidants are produced by
SSF. The process begins by activating the fungal strain on potato dextrose agar
medium for sporulation (3-4 days at 30ºC), which were then collected in a sus-
pension employing the detergent (0.01% Tween 80) and counted in a Neubauer
chamber. Each fermentation batch inoculated at 60 millions of spores per gram of
solid support. The dehydrated and pulverized plant material was 70% moisten with
a minimal culture medium contained KH 2 PO 4 , MgSO 4 and NaCl. This wet material
was referred as solid support and contains the rest of the nutrients for fungal growth.
It is important to note that depending of the antioxidant required, the specified plant
material was selected. We explored pomegranate husk for ellagic acid, and creosote
bush for NDGA.
SSF is generally performed using several bioreactors, including aluminium trays,
polystyrene plates, glass columns, steel columns or polyethylene bags. Inappropriate
setup in bioprocesses may result into the contamination. A kinetic study of antiox-
idant production is always required to establish the culture conditions including