largely through submerged-state fermentation,
and the conditions related to bioreactor production are quite comparable to processes
using terrestrial strains. Specific studies for
establishing strategies of marine enzyme purification are scarce; the same holds true for processes of secondary metabolite production.
The approach to bring marine fungi into
biotechnological application is similar to other
microbial processes: After the optimum culture
conditions are defined on a small scale (in general, Erlenmeyer flasks in shaking conditions
are used), the cultivation has to be transferred
to bioreactor-based systems and subsequent
scale-up must be performed. Substrate consumption, product formation, and cellular biomass are important factors, which should be
considered, and quantified, for appropriate
scale-up studies. Special attention in fungal
production processes has to be given to pellet
formation (Krull et al. 2013).
Generally, the unique features of marine
environment do have relevance to marine fungal biotechnology. A consideration of the
unique properties of the marine environment
is important for marine biotechnology: Biotechnological production processes are influenced by the special adaptations of organisms
to their environment. The physical factors relevant for cultivation that influence the growth of
marine fungi most are salinity (including low
water potential, high concentrations of sodium
ions and high osmotic pressure), slightly alkaline pH, partly oligotrophic nutrient conditions (especially in the water column), and
high hydrostatic pressure in combination
with low temperature, especially in the deepsea environments (Richards et al. 2012;
Bonugli-Santos et al. 2015). Sea water in average has a salinity of 33–35 ppt. Freshwater in
comparison contains less than 0.5 ppt salts. Sea
waters in estuaries and brackish areas, like in
the Baltic Sea or in river deltas, can show wide
salinity gradients, requiring special adaptation
of the inhabiting organisms. Also, hypersaline
waters occur, e.g., in the Dead Sea with salinities of 50–100 ppt. The presence of high levels
of salt in seawater are challenging with respect
to classical performance of biotechnological
processes in stainless steel vessels, as corrosion
becomes a severe issue. Even more, early
experiments demonstrated that salinity optima
for growth in some marine fungi show upward
shifts with increasing incubation temperature
(Damare and Raghukumar 2008). This interaction of salinity and temperature is termed
Phoma pattern since it was first described in
the marine species of Phoma (Lorenz and Molitoris 1990). Interestingly, only few reports have
investigated the impact of varying salt concentrations on production of marine fungal metabolites. Initial findings show that some marine
fungal species exhibit increased growth with
increasing seawater concentration in the
medium (Masuma et al. 2001). In addition to
the osmotic effects on the cell, secondary
metabolite production might be sensitive to
the seawater composition, i.e., concentration
of specific salts, which could have implications
for tank reactor cultivation of marine fungi.
In contrast to terrestrial fungi, which generally grow best at pH 4.5–6.0, marine fungi
were demonstrated to grow and produce various extracellular enzymes at pH 7–8 (Damare
et al. 2006; Raghukumar et al. 2004a). Accordingly, the pH-control in biotechnological processes will need adaptations, when marine
strains of a well-known terrestrial species are
cultivated. Pressurized conditions are of importance for the cultivation of deep-sea fungi. Low
temperature optima in combination with high
pressures are of interest, as the catalytic properties of enzymes may be altered (Eisenmenger
and Reyes-De-Corcuera 2009).
Bioprocess engineering in marine biotechnology follows the path from discovery to commercialization with a variety of possible
starting points, but a full value chain remains
mainly theoretical, as quantitative biotechnological engineering studies on marine fungi
are virtually non-existing in the literature. Silber et al. (2016) reviewed the biotechnological
realization of marine fungal antibiotics and
demonstrated that biotechnology has a vast
potential for sustainable production of antibiotics. Biotechnology, as studied and developed
with terrestrial representatives, may help to
expand and understand the chemical space in
a targeted manner, provide classical full fermentative and semi-synthetic processes, and
16 Biotechnology of Marine Fungi: New Workhorses and Applications
407
and the conditions related to bioreactor production are quite comparable to processes
using terrestrial strains. Specific studies for
establishing strategies of marine enzyme purification are scarce; the same holds true for processes of secondary metabolite production.
The approach to bring marine fungi into
biotechnological application is similar to other
microbial processes: After the optimum culture
conditions are defined on a small scale (in general, Erlenmeyer flasks in shaking conditions
are used), the cultivation has to be transferred
to bioreactor-based systems and subsequent
scale-up must be performed. Substrate consumption, product formation, and cellular biomass are important factors, which should be
considered, and quantified, for appropriate
scale-up studies. Special attention in fungal
production processes has to be given to pellet
formation (Krull et al. 2013).
Generally, the unique features of marine
environment do have relevance to marine fungal biotechnology. A consideration of the
unique properties of the marine environment
is important for marine biotechnology: Biotechnological production processes are influenced by the special adaptations of organisms
to their environment. The physical factors relevant for cultivation that influence the growth of
marine fungi most are salinity (including low
water potential, high concentrations of sodium
ions and high osmotic pressure), slightly alkaline pH, partly oligotrophic nutrient conditions (especially in the water column), and
high hydrostatic pressure in combination
with low temperature, especially in the deepsea environments (Richards et al. 2012;
Bonugli-Santos et al. 2015). Sea water in average has a salinity of 33–35 ppt. Freshwater in
comparison contains less than 0.5 ppt salts. Sea
waters in estuaries and brackish areas, like in
the Baltic Sea or in river deltas, can show wide
salinity gradients, requiring special adaptation
of the inhabiting organisms. Also, hypersaline
waters occur, e.g., in the Dead Sea with salinities of 50–100 ppt. The presence of high levels
of salt in seawater are challenging with respect
to classical performance of biotechnological
processes in stainless steel vessels, as corrosion
becomes a severe issue. Even more, early
experiments demonstrated that salinity optima
for growth in some marine fungi show upward
shifts with increasing incubation temperature
(Damare and Raghukumar 2008). This interaction of salinity and temperature is termed
Phoma pattern since it was first described in
the marine species of Phoma (Lorenz and Molitoris 1990). Interestingly, only few reports have
investigated the impact of varying salt concentrations on production of marine fungal metabolites. Initial findings show that some marine
fungal species exhibit increased growth with
increasing seawater concentration in the
medium (Masuma et al. 2001). In addition to
the osmotic effects on the cell, secondary
metabolite production might be sensitive to
the seawater composition, i.e., concentration
of specific salts, which could have implications
for tank reactor cultivation of marine fungi.
In contrast to terrestrial fungi, which generally grow best at pH 4.5–6.0, marine fungi
were demonstrated to grow and produce various extracellular enzymes at pH 7–8 (Damare
et al. 2006; Raghukumar et al. 2004a). Accordingly, the pH-control in biotechnological processes will need adaptations, when marine
strains of a well-known terrestrial species are
cultivated. Pressurized conditions are of importance for the cultivation of deep-sea fungi. Low
temperature optima in combination with high
pressures are of interest, as the catalytic properties of enzymes may be altered (Eisenmenger
and Reyes-De-Corcuera 2009).
Bioprocess engineering in marine biotechnology follows the path from discovery to commercialization with a variety of possible
starting points, but a full value chain remains
mainly theoretical, as quantitative biotechnological engineering studies on marine fungi
are virtually non-existing in the literature. Silber et al. (2016) reviewed the biotechnological
realization of marine fungal antibiotics and
demonstrated that biotechnology has a vast
potential for sustainable production of antibiotics. Biotechnology, as studied and developed
with terrestrial representatives, may help to
expand and understand the chemical space in
a targeted manner, provide classical full fermentative and semi-synthetic processes, and
16 Biotechnology of Marine Fungi: New Workhorses and Applications
407