with colored enzyme reactions in such a way that strain improvement is done in
very similar conditions to their practical application.
11.6 Online Process Control of Enzyme Production by SSF
Bulock et al. (1965) observed that Penicillium cultures had ‘‘two successive
physiological phases … the first, or trophophase, (and) the second, … or idiophase.’’ In the first phase, exponential growth occurred. In the second phase,
secondary metabolism was dominant and gave rise to the formation of conidia.
Ikasari and Mitchell (2000) found that those two phases can be related to an initial
exponential increase of the respiration rate, followed by an exponential decay.
This was confirmed by Lareo et al. (2006). Thus, the transition from trophophase
to idiophase can be followed by respiratory curves. Also, enzymes produced
during the first phase are often destroyed to be recycled as nitrogen sources in the
second phase and this fact makes important to control the physiological state of an
SSF process by the oxygen uptake rate (OUR) and the carbon dioxide production
rate (CPR). Therefore, online process control of SSF process helps to assess the
quality and extent of enzyme production. Furthermore, it has been shown that
online respirometry is a good way to estimate the heat balance of the whole culture,
because substrate oxidation is necessarily associated to heat dissipation (SaucedoCastañeda et al. 1990). This approach of process control was established more than
30 years ago in SmF processes. But it took some years to adapt online respirometry
to SSF processes. Saucedo-Castañeda et al. (1994) stated ‘‘the lack of such facilities
(online respiratory monitoring) has been, in part, responsible for the neglect of SSF
processes up to 1980 in Western and European countries.’’ Online respirometry has
been applied to monitor the production of, b-N-acetylhexosaminidase of Verticillium lecanii (Matsumoto et al. 2004), lipase of Rhizopus homothallicus (Rodríguez
et al. 2006) and lactase of Kluyveromyces marxianus (Tovar-Castro et al. 2008).
Furthermore, the data acquisition system has been improved (Chinn et al. 2003)
together with advanced programming analytic techniques (Araya et al. 2007) and
the use of sensors and alternative measurements has been reviewed and discussed
by Bellon-Maurel et al. (2003). The use of NMR imaging and respirometry of
A. oryzae cultured on wheat kernels, showed the complex diffusional and physiological processes involved in SSF cultures (Hoogschagen et al. 2001). Altogether
the instrumentation and analytical past limitations of SSF processes have been
overcome with alternatives for advanced process control.
11.7 Using SSF Solids as Crude Enzyme Preparations
Reduction of downstream processing in SSF operations include the use of
fermented solids, either wet or dry, in a variety of applications. This way,
expensive treatment of fermentation waste waters is avoided and energy
332
G. Viniegra-González
very similar conditions to their practical application.
11.6 Online Process Control of Enzyme Production by SSF
Bulock et al. (1965) observed that Penicillium cultures had ‘‘two successive
physiological phases … the first, or trophophase, (and) the second, … or idiophase.’’ In the first phase, exponential growth occurred. In the second phase,
secondary metabolism was dominant and gave rise to the formation of conidia.
Ikasari and Mitchell (2000) found that those two phases can be related to an initial
exponential increase of the respiration rate, followed by an exponential decay.
This was confirmed by Lareo et al. (2006). Thus, the transition from trophophase
to idiophase can be followed by respiratory curves. Also, enzymes produced
during the first phase are often destroyed to be recycled as nitrogen sources in the
second phase and this fact makes important to control the physiological state of an
SSF process by the oxygen uptake rate (OUR) and the carbon dioxide production
rate (CPR). Therefore, online process control of SSF process helps to assess the
quality and extent of enzyme production. Furthermore, it has been shown that
online respirometry is a good way to estimate the heat balance of the whole culture,
because substrate oxidation is necessarily associated to heat dissipation (SaucedoCastañeda et al. 1990). This approach of process control was established more than
30 years ago in SmF processes. But it took some years to adapt online respirometry
to SSF processes. Saucedo-Castañeda et al. (1994) stated ‘‘the lack of such facilities
(online respiratory monitoring) has been, in part, responsible for the neglect of SSF
processes up to 1980 in Western and European countries.’’ Online respirometry has
been applied to monitor the production of, b-N-acetylhexosaminidase of Verticillium lecanii (Matsumoto et al. 2004), lipase of Rhizopus homothallicus (Rodríguez
et al. 2006) and lactase of Kluyveromyces marxianus (Tovar-Castro et al. 2008).
Furthermore, the data acquisition system has been improved (Chinn et al. 2003)
together with advanced programming analytic techniques (Araya et al. 2007) and
the use of sensors and alternative measurements has been reviewed and discussed
by Bellon-Maurel et al. (2003). The use of NMR imaging and respirometry of
A. oryzae cultured on wheat kernels, showed the complex diffusional and physiological processes involved in SSF cultures (Hoogschagen et al. 2001). Altogether
the instrumentation and analytical past limitations of SSF processes have been
overcome with alternatives for advanced process control.
11.7 Using SSF Solids as Crude Enzyme Preparations
Reduction of downstream processing in SSF operations include the use of
fermented solids, either wet or dry, in a variety of applications. This way,
expensive treatment of fermentation waste waters is avoided and energy
332
G. Viniegra-González