26
One of the major advantages of SSF is the possibility of using the fermented
substrate as such in wet or dry form as the enzyme (Zhuang et al. 2007; Singhania
et al. 2015). The elimination of the downstream processing step can result in significant cost reductions, but has other disadvantages like carryover of the spores/mycelia to the biomass hydrolysis step (leading to contamination and lower productivity)
and the increase in solids loading in the hydrolysis reactor leading to inefficient
mixing. Apparently, the choice of direct use of fermented material as enzyme or
after extraction and removal of the fungal spores/mycelia depends on the conditions
of hydrolysis. The latter, if performed at higher temperatures, can kill the mycelia
and may prevent spore germination. Major disadvantages of SSF for cellulase production include the common disadvantages of SSF, which are the challenges in
product purification, inability for complete automation and online monitoring of
cell growth and enzyme production, providing heat and mass transfer, difficulty in
mixing, necessity to keep the moisture content optimum, increased possibility for
contamination (since SSF systems are not fully closed systems), etc. Moreover,
heterogeneity and batch variations in solid substrates can have a serious impact on
reproducibility. Also there are issues with scalability, with tray reactors occupying
a large footprint compared to similar capacity SmF systems. Nevertheless, for production of enzymes like that used for biomass hydrolysis where purity is not a major
concern, SSF systems might hold promise, since the enzymes produced on the same
substrates to be used as feedstock for biofuels can yield enzymes which are more
appropriate for the job, and at higher concentrations. The methodology also has the
process advantages of lower water and energy consumption, reduced waste stream,
less capital infrastructure, and the ability to use semiskilled labor (Zhuang et al.
2007). Recent reviews on the application of SSF technology for biomass- hydrolyzing
enzymes may be found in Yoon et al. (2014), Farinas (2015), and Behera and Ray
(2016).
Fig. 1.7 Solid-State Fermentation Facility (Koji) Room (Courtesy – CSIR-NIIST, Trivandrum,
India) Koji Room (SSF chamber) showing steel racks for keeping trays and climate control system.
Trays showing fully grown Penicillium janthinellum culture ready for harvest (for cellulase
production)
R.K. Sukumaran et al.
One of the major advantages of SSF is the possibility of using the fermented
substrate as such in wet or dry form as the enzyme (Zhuang et al. 2007; Singhania
et al. 2015). The elimination of the downstream processing step can result in significant cost reductions, but has other disadvantages like carryover of the spores/mycelia to the biomass hydrolysis step (leading to contamination and lower productivity)
and the increase in solids loading in the hydrolysis reactor leading to inefficient
mixing. Apparently, the choice of direct use of fermented material as enzyme or
after extraction and removal of the fungal spores/mycelia depends on the conditions
of hydrolysis. The latter, if performed at higher temperatures, can kill the mycelia
and may prevent spore germination. Major disadvantages of SSF for cellulase production include the common disadvantages of SSF, which are the challenges in
product purification, inability for complete automation and online monitoring of
cell growth and enzyme production, providing heat and mass transfer, difficulty in
mixing, necessity to keep the moisture content optimum, increased possibility for
contamination (since SSF systems are not fully closed systems), etc. Moreover,
heterogeneity and batch variations in solid substrates can have a serious impact on
reproducibility. Also there are issues with scalability, with tray reactors occupying
a large footprint compared to similar capacity SmF systems. Nevertheless, for production of enzymes like that used for biomass hydrolysis where purity is not a major
concern, SSF systems might hold promise, since the enzymes produced on the same
substrates to be used as feedstock for biofuels can yield enzymes which are more
appropriate for the job, and at higher concentrations. The methodology also has the
process advantages of lower water and energy consumption, reduced waste stream,
less capital infrastructure, and the ability to use semiskilled labor (Zhuang et al.
2007). Recent reviews on the application of SSF technology for biomass- hydrolyzing
enzymes may be found in Yoon et al. (2014), Farinas (2015), and Behera and Ray
(2016).
Fig. 1.7 Solid-State Fermentation Facility (Koji) Room (Courtesy – CSIR-NIIST, Trivandrum,
India) Koji Room (SSF chamber) showing steel racks for keeping trays and climate control system.
Trays showing fully grown Penicillium janthinellum culture ready for harvest (for cellulase
production)
R.K. Sukumaran et al.