Agarase is a promising biocatalyst for several industrial
applications. Agarase production was evaluated by
the marine fungus Dendryphiella arenaria utilizing Palisada
perforata as a basal substrate in semi-solid state fermentation.
Seaweed biomass, glucose, and sucrose were the most significant
parameters affecting agarase production, and their levels
were further optimized using Box-Behnken design. The maximum
agarase activity was 7.69 U/mL. Agarase showed a
degree of thermostability with half-life of 99 min at 40 °C,
and declining to 44.72 min at 80 °C. Thermodynamics suggested
an important process of protein aggregation during
thermal inactivation. Additionally, the enzymatic saccharification
of the seaweed biomass using crude agarase was optimized
with respect to biomass particle size, solid/liquid ratio,
and enzyme loadings. The amount of biosugars obtained after
optimization was 26.15 ± 1.43 mg/g. To the best of our knowledge,
this is the first report on optimization of agarase in
D. arenaria.

Alginate was recovered from Sargassum latifolium biomass using different conditions of alkali treatment.Box-Behnken experimental design was evaluated to study the influence of alkali:alga ratio, temperatureand time on alginate yield, and its molecular weight (MW) and mannuronic/guluronic acid ratio (M/G).The second-order polynomial equations were analyzed by appropriate statistical methods. Extractiontemperature and time were the most important factors during alginate alkaline extraction. MW andM/G ratio played an important role in controlling the reducing power of alginate. Increasing pH of thealginate solutions enhanced its reducing capacity, while thermal treatment showed a negative effect.Additionally, alginate exhibited good emulsion stabilizing capacities with diverse hydrophobic com-pounds. Emulsifying activity was less sensitive to temperature, ionic strength and more stable at acidicpH.

The goal of this study was to characterize diversity of fungal biota in soil, roots and green leaves of onion plant. Seventy- nine fungal species belonging to 32 genera were isolated from soil (29 genera and 72 species), rhizosphere (25 and 52), rhizoplane (24 and 38), phyllosphere (17 and 41) and phylloplane (17 and 35) on PDA medium at 19º and 28ºC. The number of fungal genera and species in soil was higher than those on roots and leaves, while those on the surface of roots (rhizosphere) or leaves (phyllosphere) were higher than those adhering to roots (rhizoplane) or leaves (phylloplane). Aspergillus (A. niger and A. terreus), followed by Penicillium (P. funiculosum and P. chrysogenum), Rhizopus (R. stolonifer) and Fusarium (F. oxysporum) were the most common fungi. A new record species is reported for the first time to Egypt namely, Zopfiella latipes (from phylloplane of onion).

There is a growing demand for chitosan production from fungi as it provides superior physico-chemical properties over traditional crustacean sources. Chitosan was recovered from Aspergillus niger biomass using different conditions of alkali deproteinization and Box-Benhken experimental design was evaluated to study the influence of alkali concentration, temperature and time on chitosan yield, degree of deacetylation (DD) and molecular weight (MW). Chitosan with different physico-chemical properties was obtained under different combinations of extraction factors. Desirability function was then used to predict the best overall combinations of responses. The most desirable compromise allowed for the recovery of chitosan with a yield of 7.0% (w/w), DD 83.64% and MW 2.70 × 104 Da, which were in good agreement with the predicted values. The recovered chitosan exhibited a good hydroxyl radical scavenging activity and ferrous ions chelating ability reached to 82.40% and 87.23%, respectively. Additionally, it demonstrated good emulsion stabilizing capacities with different vegetable oils. The results suggest that fungal mycelia can be used as a promising source of chitosan with important physico-chemical properties suitable for several applications such as food, pharmaceutical, and cosmetic industries.

Fucoidanase and alginate lyase are promising biocatalysts for several biotechnological applications. The sequentially extracted fucoidan and alginate from the brown macroalgae Sargassum latifolium were used for the optimization of a cost-effective culture medium for fucoidanase and alginate lyase production by the marine fungus Dendryphiella arenaria. Plackett–Burman statistical design was conducted for initial determination of the importance of 11 independent variables on enzyme potentiation, and the significant variables were further optimized using Box–Behnken design. The optimum conditions for fucoidanase production were fucoidan (1.5% w/v), NaCl (1.5%), urea (0.3%), and incubation period (2 days), which gives ~ 4 U mL−1 of crude fucoidanase. While, alginate (1.5% w/v), NaCl (4%), NH4Cl (0.3%), and incubation period (6 days) were the optimum conditions that enhanced alginate lyase production to ~ 24 U mL−1. Additionally, a new protocol for the enzymatic saccharification of fucoidan and alginate was optimized using Box–Behnken design with respect to substrate concentration, enzyme dosage, and temperature. The enzymatic saccharification of citric acid-extracted fucoidan gave a maximum yield of reducing sugar 365 mg g−1 fucoidan, while the alkali-extracted alginate gave 439.66 mg g−1 alginate. The results showed that the two enzymes could be exploited for the efficient production of reducing sugars from fucoidan and alginate, which are the key substrate for producing biofuels from brown macroalgal biomass.

Fucoidanase is a promising biocatalyst for several biotechnological applications. Crude fucoidanase production by Dendryphiella arenaria was optimized using a natural low-cost medium composed of Cystoseira trinodis and natural seawater. The results showed that seaweed biomass concentration and incubation period were the most significant factors affecting fucoidanase production. At the optimized conditions [seaweed biomass (4.25% w/v), seawater concentration (100% v/v), and incubation period (2 days)], the fucoidanase production was 3.43 U/mL. The crude fucoidanase exhibited a wide pH (3–9) stability with residual activity > 58%. The enzyme showed a good thermostability at 40 and 50 °C with half-lives of 239.02 and 115.52 min, respectively. Several parameters of thermal inactivation kinetics and thermodynamics were calculated, and suggested that the enzyme would be thermostable. Additionally, enzymatic extract containing fucoidanase was used for the enzymatic saccharification of the brown algal biomass in terms of seaweed particle size, solid/liquid ratio, and enzyme dosage. The maximum reducing sugars obtained was 57.11 mg/g. To the best of our knowledge, this is the first report regarding fungal fucoidanase optimization mediated saccharification of a brown seaweed.

Agarase is a promising biocatalyst that catalyze the hydrolysis of agar or agarose and produce oligosaccharides with several biotechnological applications. Agarase production by Dendryphiella arenaria was optimized using a natural low-cost medium composed of the red alga Palisada perforata and natural seawater. The results showed that seaweed biomass and seawater concentrations were the most important factors influencing agarase production. After optimization, the agarase activity was enhanced to 2.5 ± 0.3 U/mL. The crude agarase exhibited a wide pH (4‒10) stability with residual activity more than 75%. The enzyme showed high thermostability at 40 °C, and a moderate thermostability at 50, 60, 70 °C. Several parameters of thermal inactivation kinetics and thermodynamics were calculated, and suggested that the enzyme would be thermostable. Enzymatic saccharification of alkali extracted polysaccharides from the red macroalgal biomass was also optimized with respect to substrate concentration, enzyme dosage, and temperature and proceeded optimally at 0.15% substrate, 40 °C with enzyme dosage 0.9 mL/mL substrate. Under these conditions, the enzymatic saccharification yielded 647.96 mg reducing sugars/g substrate. This study therefore describes an improved, effective, and low-cost process for agarase and fermentable sugar production from seaweed biomass.

The seaweed Cystoseira trinodis was fermented by different fungi prior to extraction of fucoidan and alginate to enhance their antioxidative potential. All the investigated fungi were able to produce fucoidanase (1.05–3.41 U/ml) and alginate lyase (7.27–18.59 U/mL). Different fungal species induced a reduction in the molecular weight (MW) of fucoidan and alginate in comparison to the unfermented control. The MW of fucoidan reduced by 41–81.5%, while the MW of alginate was reduced by 28–75%, depending on the fungal species. Significant increases in the fucose and sulphate contents of fucoidan and mannuronic/guluronic acid ratio of alginate were induced by fungal fermentation. Fungal pretreatment enhanced the ferric reducing antioxidant power, total antioxidant capacity and hydroxyl radical scavenging activity of both fucoidan and alginate. Additionally, enzymatic pretreatment of the macroalgal biomass assisted in the recovery of fucoidan and alginate with low molecular weight and enhanced antioxidative potential.

Alginate and fucoidan are unique polysaccharides present in brown algae and widely used in food and
medical technologies. Alginate and fucoidan were sequentially extracted from Sargassum latifolium and
used for the preparation of alginate and alginate-fucoidan blend films with or without Ca-crosslinking.
The incorporation of fucoidan and Ca2þ decreased water solubility, but increased film thickness, water
vapor permeability and oxygen permeability. The films showed good properties against ultraviolet light,
however, incorporation of fucoidan and/or Ca2þ decreased the color parameter L* value and increased the
a* and b* values of the films. The interaction of Ca2þ and fucoidan with alginate was investigated using
FTIR analysis which confirmed the presence of hydrogen bonded interaction. Kinetics of moisture
sorption and polyphenol release exhibited a good fit to Peleg's model. Ca2þ crosslinking decreased initial
moisture sorption and increased the maximum sorption capacity of the films. Additionally, the water
vapor diffusion and polyphenol release were expressed in terms of effective diffusion coefficient based
on simplified Fick's law. The developed films showed good antioxidant properties as measured by total
antioxidant assay, ferric reducing antioxidant power and hydroxyl radical scavenging activity. Both film
type and the type of the food simulant markedly affected the polyphenol release and the antioxidant
activity of the films.

Alginate and fucoidan extracted from the brown macroalga Sargassum latifolium and chitosan derived
from the filamentous fungus Aspergillus niger were used for the development of edible films with natural
antioxidant properties. The incorporation of fucoidan and/or Ca2þ into the alginate-chitosan films
decreased water solubility, but increased film thickness, water vapor permeability and oxygen permeability.
The developed films showed good barrier properties against ultraviolet light. The interactions
between film components were investigated using FTIR analysis which confirmed the presence of
hydrogen bonded interaction. Kinetics of moisture sorption and polyphenol release exhibited a good fit
to Peleg's model. Film moisture content at equilibrium was increased by fucoidan blending. Additionally,
the water vapor diffusion and polyphenol release were expressed in terms of effective diffusion coefficient
based on simplified Fick's second law. The developed films exhibited good antioxidant properties as
measured by total antioxidant assay, ferric reducing antioxidant power and hydroxyl radical scavenging
activity. Both film type and the type of the food simulant markedly affected the polyphenol release and
the subsequent antioxidant activity of the films.