The influence of mechanical forces on the morphology and penicillin production of Penicillium chrysogenum

Mixing in the Fermentation and Cell Culture Industries

“…There are also reports that mycelial fragmentation depends on the physiological state of the microorganisms (Smith et al, 1990;Paul et al, 1994). Smith et al (1990) and Makagiansar et al (1993) proposed that the breakup frequency of mycelia would depend on (P/D 3 )(1/t c ), where P is the power input, D the impeller diameter, and 1/t c , the circulation frequency. This adaptation correlated the production rate and the morphology of the freely dispersed mycelia well at different scales up to 100 L and up to 1000 L, respectively.…”

“…These results could therefore also be used to significantly lower power input (and hence operating costs) in pelleted fermentations [k L a = 77.4P/V) 0.6 ] and obtain similar mass transfer rates as dispersed morphology fermentations [k L a = 16.7(P/V) 0.8 ]. Considering the importance of these complex morphologies on fermentation performance, and reports that changes in the morphology of P. chrysogenum can be caused by mechanical forces (Dion et al, 1954;Metz et al, 1981;van Suijdam and Metz, 1981;Smith et al, 1990;Nielsen, 1992;Makagiansar et al, 1993;Ayazi Shamlou et al, 1994;Jüsten et al, 1996Jüsten et al, , 1998a, the direct effect of agitation on morphology in submerged fermentations requires attention. As well as the total power input, the choice of impeller geometry determines the hydrodynamic forces that might affect the morphology (Jüsten et al, 1996;Amanullah et al, 1999) and differentiation (Jüsten et al, 1998a) of filamentous species, thereby influencing growth or production (König et al, 1981;Buckland et al, 1988a;Jüsten et al, 1998a;Amanullah et al, 1999).…”

“…However, provided that these factors can be controlled and optimized, agitation-induced fragmentation, apart from growth, is considered to be one of the most important factors influencing mycelial morphology (especially in the design, operation, and scale-up of fungal fermentations). Although many studies have been conducted to investigate the effects of hydrodynamic forces on mycelial morphology and productivity (Dion et al, 1954;Ujcova et al, 1980;Metz et al, 1981;van Suijdam and Metz, 1981;Reuss, 1988;Smith et al, 1990;Makagiansar et al, 1993;Ayazi Shamlou et al, 1994;Nielsen et al, 1995), they generally suffer from two limitations. First, due to the lack of suitable methods for characterizing clumps (Tucker et al, 1992), only the freely dispersed form has been considered, although it may only account for only a small fraction of the biomass (Tucker et al, 1992;Jüsten et al, 1996).…”

Secretion of heterologous and native proteins, growth and morphology in batch cultures of Aspergillus niger B1‐D at varying agitation rates

“…This is consistent with the ®ndings of some other studies, which show increased fragmentation with increases in shearing forces leading to smaller mean hyphal lengths. 23,25,26 Although there is some doubt as to the exact identity of the inducer for native glucoamylase synthesis in A niger, and thus, by extension for HEWL in this construct, with starch and oligosaccharides derived from starch. In the current medium, the presence of starch from time zero (and as evidenced by the growth of the fungus), concomitant starch degradation products, could be expected to lead to induction despite the existence of a transient spike in RS (mostly glucose [data not shown] which might lead to partial repression).…”

“…15,19,25,26 Since protein secretion has been shown to be predominantly associated with the apical regions, 27,28 any factor which impacts upon morphological form might have a signi®cant effect upon protein secretion in such organisms. This effect could be mediated indirectly, via an overall change in growth of the fungus, or, rather more directly, via change in the frequency of tip formation per unit hyphal length (ie an alteration in the relative proportion of cell mass devoted to protein synthesis).…”