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16 Bioreactors for the Production of Industrial Chemicals and Bioenergy Recovery from Waste

food grains and seeds such as wheat, oat, rice, maize, etc. Wicklow et al. reported

the production of Ochratoxin A, a known mycotoxin with established toxicity to

insects, from the sclerotia of the fungus Aspergillus carbonarius Northern Regional

Research Laboratory (NRRL) 369. The sclerotia were yielded from SSF of corn

kernels. Ochratoxin A accounted for the function of the methanol extract against

larvae of the detritivorous beetle, Carpophilus hemipterus (75% reduction in feeding

rate) and corn ear worm, Helicoverpa (50% mortality with 99% reduction in weight

gain among surviving larvae) when incorporated into a pinto bean diet at levels

less than those in the sclerotia. Gibberellins (GAs), which are a big family of iso-

prenoid plant growth hormones and most of them are bioactive growth controllers,

also control the seed germination, elongation of stem, and flowering. They have

been observed to be formed during SSF of the rice pathogen, Gibberella fujikuroi

(principal bioactive composite is gibberellic acid 3). Durand et al. and Tomasini

et al. compared SSF and submerged fermentation (SmF) for gibberellic acid

production. The G. fujikuroi produced 23 mg of gibberellin per ml in 120 hours of

liquid fermentation. The use of polyurethane as inert solid support resulted in very

poor growth of the culture. The SSF using wheat bran produced 3 g GA per 3 kg dry

substrate in 11 days. While the majority of the studies reported on a laboratory scale,

several studies have been carried out on the manufacturing of various antibiotics in

pilot SSF. These include penicillin, cephalosprin, tetracyclines, chlorotetracyclines,

oxytetracyclines, surfactin, actinorhodin, methylenomycin, monorden, etc.

16.8.2

Enzymes

The SSF can be of unique interest in those processes where the crude fermented

product may be used directly as enzyme source. Microbial enzymes will play a

major role in biotransformations concerning organic solvent media. Agro-industrial

residues are normally considered as the substrates for the enzyme production in

SSF method (Table 16.1). Wheat bran is the key substrate and has been exploited

normally in a range of processes. The SSF is mostly suitable for the production of

lignocellulosic enzymes for a variety of agro-biotechnological applications. In SmF,

yields of cellulase are usually about 10 g/l, and the usual fermentation expenditure

in a stirred tank bioreactor is about $200/m³. Thus, the manufacturing cost in the

crude fermentation by SmF is about $20/kg. In SSF average production level is

about 10 mg/g substrate and the normal fermentation expenditure is only about

US$ 25/mt. Thus, the unit price of SSF cellulase is just about $0.2/kg. Similar

types of results were obtained for xylanase production in laboratory scale stirred

tank bioreactor [31]. More published information is obtainable on the production

of enzymes of industrial importance, such as proteases, cellulases, ligninases,

xylanases, pectinases, amylases, glucoamylases, etc. by SSF. Alltech (Nicholasville,

KY, USA) has been recognized as a large-scale enzyme-manufacturing company.

Alltech’s European Bioscience Centre, in colaboration with Institut National de la

Recherche Agronomique (INRA), the French government’s agricultural research

institution, has been implicated in the fermenter configuration for the production

of phytase.