3.5.6 Moisture Content
Moisture content plays an imperative function in the SSF system. The initial
moisture level influences solid substrate affecting aeration, nutrients solubility,
heat and gas transfers, and substrate swelling by microorganisms (Ellaiah et al.
2004). The moisture content demands in SSF vary based on enzyme produced,
substrate, and microbe, particle size of substrate as well as the pattern of particles
(Kalogeris et al. 2003). The decrease in enzyme activities at higher initial moisture
level might be a steric impediment in inter-particular spaces and impair oxygen
transport (Sandhya and Lonsane 1994).
The elevated moisture level improved fungal growth and cellulolytic enzymes
production when agro-wastes were carbon sources during SSF (Kalogeris et al.
2003; Panagiotou et al. 2003). Lesser moisture content leads to less growth, a
lower level of substrate enlargement, and higher surface area, while higher moisture
content decline porosity, which would affect lesser oxygen transfer, heat dissolution,
and improved development of aerial mycelium respectively. Moisture level in solid
substrate influences aeration and nutrients solubility which is essential to sustain
organism’s growth and metabolites (Ahmed 2008).
Hassan et al. (2016) reported that hydrolytic enzyme production was improved
with rising the moisture level in sugarcane bagasse pith by A. oryzae FK-923 and
higher production of enzymes were recorded when moisture level was 80% and
enzyme production with 96.4, 98.2, 118.2, and 625.6 U/g for FPase, CMCase,
β-glucosidase, and xylanase, respectively. Hassan et al. (2016) found 70% moisture
for cellulase production on rice grass with Aspergillus sp. SEMCC-3248 in SSF.
Zhao et al. (2011) evidenced 75% moisture was used for the synthesis of cellulase in
SSF by T. reesei SEMCC-3217. Kim et al. (2014) observed that 40–50% moisture
was best for production of cellulases by Penicillium sp. in SSF of oil palm empty
fruit bunch. But, more water in the medium could create clumping of medium,
hinder aeration, and growth of hyphae, which could also effect in decline production
of an enzyme (Gao et al. 2008).
The best moisture level for higher cellulase production with T. reesei mutant was
observed to be 55–70%, but T. reesei Rut C30 was evidenced to produce cellulase
maximum at 79% of moisture content (Das et al. 2008). Enhancement of initial
moisture level from 60 to 80% in actual fact increased the enzyme activity and higher
enzyme activity was attained with 80% moisture level (Gao et al. 2008). When
moisture level is lower than the demand level, the solubility of nutrients is narrow
and it hampers the efficient nutrients take-up with fungi (Kumar et al. 2011). On
contrary, when the moisture level is very high, particles of substrate were bound with
a thick layer of water. As a result, particles are likely to attach collectively wherein
this confines air diffusion among particles and surrounding (Deswal et al. 2011).
Additionally, the risk of contamination is larger if higher moisture level is used in
SSF as situation supports the growth of hostile microbes. The sum of moisture
required is straightly connected to the structure of lignocellulosic substrate. The
porosity and specific surface area of solid particles administer the effectiveness of air
3 Influence of Significant Parameters on Cellulase Production by Solid-State. . .
85
Moisture content plays an imperative function in the SSF system. The initial
moisture level influences solid substrate affecting aeration, nutrients solubility,
heat and gas transfers, and substrate swelling by microorganisms (Ellaiah et al.
2004). The moisture content demands in SSF vary based on enzyme produced,
substrate, and microbe, particle size of substrate as well as the pattern of particles
(Kalogeris et al. 2003). The decrease in enzyme activities at higher initial moisture
level might be a steric impediment in inter-particular spaces and impair oxygen
transport (Sandhya and Lonsane 1994).
The elevated moisture level improved fungal growth and cellulolytic enzymes
production when agro-wastes were carbon sources during SSF (Kalogeris et al.
2003; Panagiotou et al. 2003). Lesser moisture content leads to less growth, a
lower level of substrate enlargement, and higher surface area, while higher moisture
content decline porosity, which would affect lesser oxygen transfer, heat dissolution,
and improved development of aerial mycelium respectively. Moisture level in solid
substrate influences aeration and nutrients solubility which is essential to sustain
organism’s growth and metabolites (Ahmed 2008).
Hassan et al. (2016) reported that hydrolytic enzyme production was improved
with rising the moisture level in sugarcane bagasse pith by A. oryzae FK-923 and
higher production of enzymes were recorded when moisture level was 80% and
enzyme production with 96.4, 98.2, 118.2, and 625.6 U/g for FPase, CMCase,
β-glucosidase, and xylanase, respectively. Hassan et al. (2016) found 70% moisture
for cellulase production on rice grass with Aspergillus sp. SEMCC-3248 in SSF.
Zhao et al. (2011) evidenced 75% moisture was used for the synthesis of cellulase in
SSF by T. reesei SEMCC-3217. Kim et al. (2014) observed that 40–50% moisture
was best for production of cellulases by Penicillium sp. in SSF of oil palm empty
fruit bunch. But, more water in the medium could create clumping of medium,
hinder aeration, and growth of hyphae, which could also effect in decline production
of an enzyme (Gao et al. 2008).
The best moisture level for higher cellulase production with T. reesei mutant was
observed to be 55–70%, but T. reesei Rut C30 was evidenced to produce cellulase
maximum at 79% of moisture content (Das et al. 2008). Enhancement of initial
moisture level from 60 to 80% in actual fact increased the enzyme activity and higher
enzyme activity was attained with 80% moisture level (Gao et al. 2008). When
moisture level is lower than the demand level, the solubility of nutrients is narrow
and it hampers the efficient nutrients take-up with fungi (Kumar et al. 2011). On
contrary, when the moisture level is very high, particles of substrate were bound with
a thick layer of water. As a result, particles are likely to attach collectively wherein
this confines air diffusion among particles and surrounding (Deswal et al. 2011).
Additionally, the risk of contamination is larger if higher moisture level is used in
SSF as situation supports the growth of hostile microbes. The sum of moisture
required is straightly connected to the structure of lignocellulosic substrate. The
porosity and specific surface area of solid particles administer the effectiveness of air
3 Influence of Significant Parameters on Cellulase Production by Solid-State. . .
85