Marco Nemesio E. Montaño

Structure and functional performance of gigartinacean kappa -iota hybrid carrageenan and solieriacean kappa -iota carrageenan blends

Abstract Hybrids of kappa and iota carrageenans, known as kappa-2 carrageenans, of contrasting phycological origin and type of hybridization were compared chemically and functionally. Nuclear magnetic resonance spectrometry showed gigartinacean kappa-2 (hybridization was known to be a co-occurrence of kappa and iota structures in a chain) to contain 45% iota and 55% kappa, very similar to a 3:3 kappa:iota hand-made blend of solieriacean origin (hybridization was that kappa and iota occurring as separate chains). Gel permeation chromatographic data, however, demonstrated the gigartinacean extract to possess lower molecular weight compared to the solieriacean extracts, a hint to the variability in the origin of the two hybrid carrageenans. As texturing agents in water and milk systems, gigartinacean kappa-2 was found to produce inferior gels compared to its hand-made counterpart. However, both hybrids were found to exhibit similar functional performance as viscosity-enhancing/stabilizing agent in hot-processed chocolate milk preparations, and analogous inutility as viscosity build-up agent in cold-processed chocolate milk. A hand-made solieriacean kappa–iota blend can have the same properties as a gigartinacean kappa-2, but it depends on the actual application which blend performs comparable to kappa-2.

Bioremediation potential of three carrageenophytes cultivated in tanks with seawater from fish farms

Intensive fish farming discharges large amount of nutrients, the majority of which are composed of dissolved nitrogen in ammonium form, which promotes eutrophication in coastal waters. Macroalgae have been proven to effectively reduce the nutrients of fish farm effluents and at the same time increase the economic output of the aquaculture system when economically important species are utilized. In this study, the potential of three high value carrageenophytes (Kappaphycus alvarezii, Kappaphycus sp., K. striatum) to extract ammonium in fish farm effluent collected from a milkfish (Chanos chanos) fish cage was investigated. To establish economic viability of the integrated culture system, the effects of elevated total ammonia of fish farm effluent on the growth rate, phycocolloid content, and quality of these seaweeds were determined. Tank cultivation trials showed that the three carrageenophytes substantially reduced the ammonium content of the fish farm effluent (41–66% reduction efficiency) and consequently attained maximum daily growth rates of 4.41%, 2.90%, and 2.75% for K. striatum, Kappaphycus sp., and K. alvarezii, respectively. Their carrageenan content was improved. Carrageenan quality, however, was not significantly enhanced. Elevated ammonium in fish farm effluent did not adversely affect the performance of tank cultivated Kappaphycus; thus, future integration of these seaweeds in fish farms is feasible.

Stability of agar in the seaweed Gracilaria eucheumatoides (Gracilariales, Rhodophyta) during postharvest storage

The status of the cell-wall polysaccharide of the red seaweed, Gracilaria eucheumatoides upon postharvest storage was assessed in this study. The yield, chemical composition, physical and textural properties of alkali-treated agar extract was determined at different time intervals within 31 months of storage at dried state after harvest. Minimal fluctuation in agar yield was observed, ranging from 22.9% to 29.0%. The gel strength of agar extracts averaged 318gcm(-2) until the third month of storage but decreased considerably thereafter. The relative viscosity and molecular weight of the extracts varied inversely with storage time. Results indicated that both physical and textural parameters of agar generally decreased with storage time, likely due to depolymerization as indicated by decrease in molecular weight. Agar extracted from seaweeds up to 3 months of storage could be considered to exhibit gel quality suitable for food applications. Prolonged storage of the seaweed harvest is not recommended.

FINE CHEMICAL STRUCTURE OF CARRAGEENAN FROM THE COMMERCIALLY CULTIVATED KAPPAPHYCUS STRIATUM (SACOL VARIETY) (SOLIERIACEAE, GIGARTINALES, RHODOPHYTA)1

The polysaccharide extracted from Kappaphycus striatum (Schmitz) Doty (sacol variety), a recently farmed eucheumoid seaweed, was characterized by Fourier transform infrared and NMR spectroscopy. The extract is composed mainly of 3‐linked β‐d‐galactopyranosyl‐4‐sulfate residues alternating with 4‐linked 3,6‐anhydro‐α‐d‐galactopyranosyl residues (κ‐carrageenan). Minor components include 3,6‐anhydrogalactopyranosyl‐2‐sulfate residues (ι‐carrageenan) and 6‐O‐methylgalactopyranosyl‐4‐sulfate residues (methylated carrageenan). The substitution pattern of carrageenan in the tribe Eucheumatoideae and the family Solieriaceae is revisited in terms of chemotaxonomic affiliation.

Thalassic biogas production from sea wrack biomass using different microbial seeds: cow manure, marine sediment and sea wrack-associated microflora.

Sea wrack (dislodged sea grasses and seaweeds) was used in biogas production. Fresh water scarcity in island communities where sea wrack could accumulate led to seawater utilization as liquid substrate. Three microbial seeds cow manure (CM), marine sediment (MS), and sea wrack-associated microflora (SWA) were explored for biogas production. The average biogas produced were 2172±156 mL (MS), 1223±308 mL (SWA) and 551±126 mL (CM). Though methane potential (396.9 mL(CH4) g(-1) volatile solid) computed from sea wrack proximate values was comparable to other feedstocks, highest methane yield was low (MS=94.33 mL(CH4) g(-1) VS). Among the microbial seeds, MS proved the best microbial source in utilizing sea wrack biomass and seawater. However, salinity (MS=42‰) observed exceeded average seawater salinity (34‰). Hence, methanogenic activity could have been inhibited. This is the first report on sea wrack biomass utilization for thalassic biogas production.

Agar from the red seaweed, Laurencia flexilis (Ceramiales, Rhodophyta) from northern Philippines

The worldwide production of the gelling agent agar mainly rely on the red algae of the order Gracilariales and Gelidiales for raw material. We investigate here the potential of a species from another red algal order, Ceramiales as an agar source. The agar from Laurencia flexilis collected in northern Philippines was extracted using native and alkali treatment procedures and the properties of the extracts were determined using chemical, spectroscopic and physical methods. The native agar, 26% dry weight basis, forms a gel with moderate gel strength (200 g cm−2). Alkali‐treatment did not enhance the gel strength, indicating insignificant amounts of galactose‐6‐sulfate residue, the precursor of the gel‐forming 3,6‐anhydrogalactose (3,6‐AG) moieties. Furthermore, the Fourier transform infrared and chemical analysis showed low sulfate and high 3,6‐AG levels, not affected significantly by the alkali treatment. Nuclear magnetic resonance spectroscopic analysis revealed 3‐linked 6‐O‐methyl‐D‐galactose and 4‐linked 3,6‐anhydro‐L‐galactose as the major repeating unit of the native extract, with minor sulfation at 4‐position of the 3‐linked galactose residues. The native and alkali treated agars have comparably high gelling and melting temperatures, whereas the former exhibits higher gel syneresis. Laurencia flexilis could be a good source of agar that possesses physico‐chemical and rheological qualities appropriate for food applications. Due to the inability of alkali treatment to enhance the key gel qualities of the native extract, it is recommended that commercial agar extraction from this seaweed would be done without pursuing this widely‐used industrial procedure.

Effects of natural gas condensate – water accommodated fraction on coral larvae

The toxic effects of the water accommodated fraction (WAF) of a natural gas condensate on the larvae of five brooding coral species of the Family Pocilloporidae were examined in short term (96 h) bioassays. Lethality was observed in some larvae of Seriatopora hystrix and Seriatopora guttatus upon exposure to high concentrations of the condensate WAF, while those of Stylophora pistillata, Pocillopora damicornis and Pocillopora verrucosa did not experience mortality. Furthermore, increasing concentrations of WAF produced either delayed or impeded metamorphosis for all species except P. damicornis. Growth of juveniles, exposed to different WAF treatments for 96 h during their larval/early juvenile stages, was measured after 30 d. Marked decrease in subsequent growth rate (polyp count) was observed for S. hystrix, S. guttatus and S. pistillata with increasing WAF concentration. The results showed differential susceptibility of larvae of closely related coral species to oil stress, with the following sensitivity ranking: S. guttatus>S. hystrix>S. pistillata>P. verrucosa>P. damicornis. Oil exposure during the planktonic, larval stage of susceptible corals can adversely affect survivorship, recruitment and/or subsequent colony growth, thereby having profound consequences for the abundance of these corals in space and time.

‘Endong’, a rare variety of the farmed carrageenophyte Eucheuma denticulatum (Burman) Collins & Hervey from the Philippines

The variety described in this paper is rather a rare and interesting one. Locally called ‘endong’, this was discovered first in a farm in Tawi-Tawi, Sulu Archipelago, Philippines. During harvest, seaweed farmers used to mix this with ‘tambalang’ (Kappaphycus alvarezii (Doty) Doty ex Silva var. tambalang Doty, the ‘cottonii’ of commerce) because of the presumption of it producing the same carrageenan type as that of ‘tambalang’, viz., kappa-carrageenan. The two farmed varieties are similar in appearance. Complaints arose from seaweed processing plants when the resulting gelling properties (hard and brittle gel) expected of the kappa-carrageenan-producing ‘tambalang’ were not met. Because of its lax habit and long, smooth, and naked basal axes, ‘endong’ was initially thought to be related to ‘tambalang’ and differ from the farmed ‘spinosum’ (Eucheuma denticulatum (Burman) Collins & Hervey) whose typical or common form has shorter axes covered from base to apex with spinous determinate (ramuli) or indeterminate branchlets arranged irregularly and in whorls at predictable interval. However, a closer look at ‘endong’ shows that it also has spinous branchlets arranged in whorls, but confined to the apical portion of the branches. Moreover, its internal axial anatomy shows rhizoidal filaments forming a core. Both characters fit well the distinguishing taxonomic criteria established for E. denticulatum. Chemical characterization of its carrageenan and the determination of its phylogenetic affinities support our morphological findings. Hence, we report and describe ‘endong’ as a rare variety, and we name it E. denticulatum (Burman) Collins & Hervey var. endong Trono & Ganzon-Fortes var. nov. Tips to distinguish ‘endong’ from ‘tambalang’ are included in this paper to aid seaweed farmers in separating the two during harvest.

Seasonal variations in the composition and gel quality of agar from Gracilaria edulis in the Philippines

Abstract Agar from Gracilaria edulis collected in the Philippines is composed primarily of a repeating disaccharide unit of 4-linked 3,6-anhydro-α-L-galactopyranose (LA) and 3-linked 6-O-methyl-β-D-galactopyranose (G6M). Chemical and spectroscopic analyses further revealed partial (19–27 mol %) methylation at O-2 of the LA residues. Sulfate was attached to O-4 of G6M and/or G, with approximately 20% of these residues bearing the substituent. No pyruvate substituent was detected. A seasonal assessment of the composition, rheological and physical properties of Gracilaria edulis agar was undertaken. Constituent sugar analysis revealed a variable degree of methylation (80–91 mol % on O-6 of the G and 19–27 mol % on O-2 of the LA residues); the highest amounts of mono-O-methylated residues (G6M and LA2M) were found in the samples collected in the dry season while the lowest was obtained during the rainy season. The sample collected during the onset of the rainy season contained the lowest amount of sulfate (2.3%) while the cold season sample contained the highest sulfate content (3.2%). Seaweed samples collected during the onset of the rainy season exhibited the highest agar yield, gel strength, deformation, cohesiveness, and melting temperature. Gracilaria edulis agar possesses gel characteristics useful in the food industry.

Enhancement of carrageenan gel quality in the commercially important tropical seaweed Eucheuma denticulatum (Rhodophyta), with postharvest treatment in low-nutrient conditions

Abstract The potential of postharvest culture in low-nutrient conditions was evaluated in terms of enhancement of carrageenan gel quality in the tropical seaweed Eucheuma denticulatum (“spinosum” of commerce) and as an alternative to industrial alkali treatment. Postharvest batch culture of seaweeds with either initially low or high nutrient concentrations (both ending with low nutrient concentrations) produced native carrageenans that had significantly higher gel strengths (48 g cm-2 in both treatments) than those treated with continuous culture in high nutrient concentrations (18 g cm-2). The gel strength of native carrageenans from batch-cultured seaweeds was also significantly higher than that of both native and alkali-treated carrageenans from seaweeds that had not undergone postharvest culture (11 and 29 g cm-2, respectively). The mechanism indicated for the enhancement of carrageenan gel quality involves stopping the production of precursor (galactose-6-sulfate) and converting the preexisting precursor to 3,6-anhydrogalactose units through in vivo enzymatic action. Postharvest batch culture with low nutrient concentrations is considered to be an eco-friendly alternative to industrial alkali treatment in the enhancement of carrageenan gel quality.