Effects of inoculum density, carbon concentration, and feeding scheme on the growth of transformed roots of Artemisia annua in a modified nutrient mist bioreactor

Towler, Melissa J.

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Effects of inoculum density, carbon concentration, and feeding scheme on the growth of transformed roots of Artemisia annua in a modified nutrient mist bioreactor

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Previous work has shown that despite the lack of oxygen limitation, transformed roots of Artemisia annua had lower biomass productivity in a nutrient mist bioreactor than in a liquid-phase bubble column reactor where the roots demonstrated metabolic signs of oxygen stress. Mathematical modeling suggested that the roots were too sparsely packed to capture mist particles efficiently and to achieve high growth rates. In this study, higher packing fractions were tested, and the growth rate increased significantly. Similarly, higher sucrose concentrations increased the growth rate. Growth kinetics for 2, 4, and 6 days showed an unexpected decrease or stationary growth rate after only 4 days for both 3% and 5% sucrose feeds. Residual media analyses indicated that carbon was not exhausted, nor were other major nutrients including phosphate. Increasing the misting frequency such that the total amount of carbon delivered from a 3% sucrose feed was equivalent to that delivered in a 5% sucrose feed showed that growth was affected by the modified cycle. These studies showed that both the concentration of carbon source and alteration of misting frequency can significantly increase growth rates of hairy roots in mist reactors.

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