sources, because non-marine strains of A. sydowii did not cause disease in sea fans (Kim and
Rypien 2015).
A wide number of fungi were described in
association with marine plants, including mangroves. On the one hand, endophytic lifestyle
seems to be quite common (Rashmi et al. 2019).
On the other hand, pathogenic, e.g., oomycetes
and chytrids frequently occurred and induced
prevalence of disease in algal aquacultures.
These infections can destroy the populations
of host plants to a great extent (Li et al. 2010),
mainly known from Asian countries cultivating
a number of algal species since long time. Frequent re-isolation of fungi and specific occurrence of fungal species in association with
specific macroorganisms point toward a number of host-microbe interactions beyond pathogenicity and opportunistic commensalism.
Cultured fungi isolated from sessile marine animals and algae have been demonstrated to be
capable of producing novel chemicals, which
have the potential to affect the marine hosts
and their microbiome (as reviewed in Imhoff
et al. 2011; Rateb and Ebel 2011; Raghukumar
2008). Also, the determination of abundant bioactive compounds of fungal origin in the holobiont indicates their roles in host-fungal and
fungal-microbe interactions.
In any case, a thorough understanding of
the roles marine fungi do have in the ecosystem
will help to prospect for novel genes and products and facilitate realization of biotechnological application of marine fungi, their enzymes,
and metabolites.
III. Biotechnology of Marine Fungi:
Challenges and Opportunities
A. Cultivation of Marine Fungi: Same But
Different?
Any biotechnological production depends on
the fungal physiology, as well as on culture
medium composition. Carbon and nitrogen
sources play an important role in biotechnological production. This is well established for
numerous fungi from terrestrial environments
and was confirmed for marine fungi. Complex
substrates, such as starch, casein, pectin, malt
extract, wheat bran, olive oil, xylan, and sugarcane bagasse, were used for the cultivation of
marine fungi from a variety of marine sources.
The optimum temperature and pH of most of
these fungi (and subsequently their enzymes)
ranges from 20 to 70
C and from 3 to 9, respectively (Kjer et al. 2010; Golubic et al. 2005; Imhoff 2016).
Marine fungal strains of genera also
described from terrestrial habitats have
approximately the same optimum conditions
for growth and use the same primary pathways
for energy and biomass production. However,
the demand of salt during cultivation can be
crucial as a consequence of adaptation to ocean
salinity (e.g., D’Souza-Ticlo et al. 2009; Chen
et al. 2011 for enzymes from marine fungi).
Salt demand means not only presence of
sodium chloride in the appropriate concentration. Sulfate, one of the major constituents of
sea water but also minor elements including
heavy metals, is equally important for proper
growth media composition of many, especially
the obligate marine fungi. Accordingly, many
researchers use “artificial sea water” for cultivation of these strains (Kjer et al. 2010; Jones
and Jennings 1964).
The diversity of marine fungi is not adequately represented in the cultured diversity.
Many studies have focused on just a few genera,
mainly Penicillium, Aspergillus, Fusarium, and
Cladosporium. This might be due to the relatively easiness of isolation of these groups,
which also dominate isolation campaigns from
terrestrial habitats. But still, even when comparing marine strains of these groups to terrestrial relatives, different secondary metabolite
biosynthesis pathways can be found (Imhoff
2016). The high diversity seen at the genus
level extends further to the subgenus level. For
example, representatives of Penicillium are
among the most studied fungi and represent
important drug producers. Nevertheless, many
new secondary metabolites are continuously
found within strains of marine origin of this
genus as shown in reviews by Rateb and Ebel
(2011) and Blunt et al. (2015). However, many
of the novel and unknown environmental fun402
A. Kramer and A. Labes
Rypien 2015).
A wide number of fungi were described in
association with marine plants, including mangroves. On the one hand, endophytic lifestyle
seems to be quite common (Rashmi et al. 2019).
On the other hand, pathogenic, e.g., oomycetes
and chytrids frequently occurred and induced
prevalence of disease in algal aquacultures.
These infections can destroy the populations
of host plants to a great extent (Li et al. 2010),
mainly known from Asian countries cultivating
a number of algal species since long time. Frequent re-isolation of fungi and specific occurrence of fungal species in association with
specific macroorganisms point toward a number of host-microbe interactions beyond pathogenicity and opportunistic commensalism.
Cultured fungi isolated from sessile marine animals and algae have been demonstrated to be
capable of producing novel chemicals, which
have the potential to affect the marine hosts
and their microbiome (as reviewed in Imhoff
et al. 2011; Rateb and Ebel 2011; Raghukumar
2008). Also, the determination of abundant bioactive compounds of fungal origin in the holobiont indicates their roles in host-fungal and
fungal-microbe interactions.
In any case, a thorough understanding of
the roles marine fungi do have in the ecosystem
will help to prospect for novel genes and products and facilitate realization of biotechnological application of marine fungi, their enzymes,
and metabolites.
III. Biotechnology of Marine Fungi:
Challenges and Opportunities
A. Cultivation of Marine Fungi: Same But
Different?
Any biotechnological production depends on
the fungal physiology, as well as on culture
medium composition. Carbon and nitrogen
sources play an important role in biotechnological production. This is well established for
numerous fungi from terrestrial environments
and was confirmed for marine fungi. Complex
substrates, such as starch, casein, pectin, malt
extract, wheat bran, olive oil, xylan, and sugarcane bagasse, were used for the cultivation of
marine fungi from a variety of marine sources.
The optimum temperature and pH of most of
these fungi (and subsequently their enzymes)
ranges from 20 to 70
C and from 3 to 9, respectively (Kjer et al. 2010; Golubic et al. 2005; Imhoff 2016).
Marine fungal strains of genera also
described from terrestrial habitats have
approximately the same optimum conditions
for growth and use the same primary pathways
for energy and biomass production. However,
the demand of salt during cultivation can be
crucial as a consequence of adaptation to ocean
salinity (e.g., D’Souza-Ticlo et al. 2009; Chen
et al. 2011 for enzymes from marine fungi).
Salt demand means not only presence of
sodium chloride in the appropriate concentration. Sulfate, one of the major constituents of
sea water but also minor elements including
heavy metals, is equally important for proper
growth media composition of many, especially
the obligate marine fungi. Accordingly, many
researchers use “artificial sea water” for cultivation of these strains (Kjer et al. 2010; Jones
and Jennings 1964).
The diversity of marine fungi is not adequately represented in the cultured diversity.
Many studies have focused on just a few genera,
mainly Penicillium, Aspergillus, Fusarium, and
Cladosporium. This might be due to the relatively easiness of isolation of these groups,
which also dominate isolation campaigns from
terrestrial habitats. But still, even when comparing marine strains of these groups to terrestrial relatives, different secondary metabolite
biosynthesis pathways can be found (Imhoff
2016). The high diversity seen at the genus
level extends further to the subgenus level. For
example, representatives of Penicillium are
among the most studied fungi and represent
important drug producers. Nevertheless, many
new secondary metabolites are continuously
found within strains of marine origin of this
genus as shown in reviews by Rateb and Ebel
(2011) and Blunt et al. (2015). However, many
of the novel and unknown environmental fun402
A. Kramer and A. Labes