Growth of hairy roots

Effects of Inoculum Conditions on Growth of Hairy Roots of Panax ginseng C.A. Meyer... 

Several bioreactor designs have been demonstrated for large-scale culture of hairy roots (6,7). Bioreactors used for hairy root culture are more complex owing to continuous growth of hairy root and must compensate for the heterogeneous, cohesive, structured, and entangled nature of fibrous roots (4). Hairy root cultures may be feasible for large-scale applications, but many problems with the hairy root culture system are still unsolved (6-9). 

Influence of Light Intensity on Photomixotrophic and Photoautotrophic Growth of Hairy Roots... 

To increase the growth of hairy roots, the influence of the sucrose concentration in the WP liquid medium was tested (Fig. 10). The fastest growth was obtained with 8% sucrose (8.91 g fresh weight after 19 days). A similar effect was observed to that described in the previous experiment, i. e. the total alkaloid content decreased with the higher sucrose concentration in the medium, whereas the amount of 7P-hydroxyhyoscyamine increased up to 0.012% dry weight in the media with 8% and 10% sucrose. The content of littorine produced by the hairy roots particularly decreased with higher sucrose concentrations in the medium. 

Bensaddek L, Villarreal ML, Hiniaux MA (2008) Induction and growth of hairy roots for the production of medicinal compounds. J Integr Biosci 3(l) 2-9... 

Fig. 7. Comparison of hairy root growth rate on inoculum size in flask culture at 15 d.

We reported that an airlift column reactor was superior for the cultivation of hairy roots, in which reticulate polyurethane foam was used as an appropriate support for the even growth and distribution of the hairy roots [44]. A turbine-blade reactor was developed by Nagai et al. [45], in which the cultivation space is separated from the agitation space by a cylindrical stainless-steel mesh and a stainless-steel plate with a slit so that hairy roots do not come into contact with the impeller. The impeller, with 8 turbine blades, is fitted in the agitation space at the bottom of the reactor. The medium flows upwards along the vessel wall, passes through the cylindrical stainless-steel mesh in the center of the re-... 

According to the morphological properties of branching and elongation, the following assumptions are made for the modeling of hairy root growth as illustrated in Fig. 7 [43] ... 

Fig. 7. Schematic drawing of hairy root branching growth...

We compared the time course of tropane alkaloid production in the adventitious and two types of hairy roots of H. albus, transformed with the different strains of A. rhizogenes [15]. In the adventitious roots of H. albus, hyoscyamine was the main alkaloid during the first 6 weeks of culture in phytohormone-free MS liquid medium. At the seventh week of culture, with the beginning of the stationary growth, scopolamine became the major constituent (Fig. 7). 

Since Kamada etal. (45) and Ohkawa etal. (46) reported that GAj enhanced the growth and alkaloid production in the hairy root culture of Datura innoxia, the effects of GAj vs lAA, IB A or NAA combinations on the growth and phenolic production were determined. The roots (ca 50 mg, fw) were inoculated in MS liquid media (50 ml / 100 ml flask) containing various combinations of GAj (0,0.001,0.01,0.1 or 1 mg/1) and 1 mg/1 lAA, IBA or NAA and cultured for 4 weeks (Table 3). In the combination with 1 mg/1 IBA or NAA, GAj strongly inhibited the growth of the roots. GAj also exhibited no prominent effect on phenolic production when 1 mg/1 lAA, IBA or NAA was present in the culture medium. 

The adventitious and hairy root cultures of S. officinalis seem to be useful not only for the production of high Mr hydrolyzable tannins such as 10 and 11 but also for biosynthetic studies. The phenolic content in the hairy roots was almost the same as that of the adventitious roots. Taking into account the rapid growth, the hairy root cultures of this plant are more valuable than its normal root cultures for the production of these phenolics. 

Ca 20 mg (fw) of hairy roots were inoculated into hormone-free 1/2 MS, 1/2 B5 and RC liquid media and cultured at 25 °C on a rotary shaker (80 rpm) in the dark. The growth rates were shown in Fig. 10. The amount of the hairy roots increased satisfactorily after week 2 in these media, particularly the growth rates observed in 1/2 B5 and 1/2 MS media were almost 3 times larger than that in RC medium. In these cultures, the hairy roots showed pale yellow colouration suggesting the enrichment of yellow pigment (xanthones) in the roots. In addition, the hairy roots were slightly bitter to the taste which indicated the presence of bitter principles. 

Hilton MG, Rhodes MJC (1990) Growth and hyoscyamine production of hairy root cultures of Datura stramonium in a modified stirred tank reactor. Appl Microbiol Biotechnol 33 132-138. 

Even if the alkaloid content is quite high, an important step in the establishment of root cultures is the selection of the best clones which combine good growth and high alkaloid production. The occurrence of clonal variations allows the selection of high-producing lines. Mano et al. [78] were able to select a clone of hairy roots of Duboisia leichhardtii, producing 2.1 % DW scopolamine, more than twice the amount found in the leaves of the non-transformed plants. 

Hairy roots are not as readily manipulated by altering culture conditions or pH as are suspension cultures. However, the effect of temperature on growth and hyoscyamine production in transformed root cultures of Datura stramonium has been demonstrated by Hilton and Rhodes [86]. Another way to enhance the secondary metabolite accumulation of hairy roots is the addition of precursors and/or metabolic intermediates to the growth medium. The addition of (R,S)- phenyllactic acid increased significantly the accumulation of hyoscyamine and scopolamine in the hairy root culture of Datura Candida x D. aurea [72]. 

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