Conference Paper
Bioavailability of Antioxidants, Minerals and Heavy Metals in Two Edible Seaweed Species: Kappaphycus alvarezii and Caulerpa racemose
  • December 2025
Research Interest Score
0.3
Citations
0
Recommendations
1
Reads
4
Conference Paper
Bioavailability of Antioxidants, Minerals and Heavy Metals in Two Edible Seaweed Species: Kappaphycus alvarezii and Caulerpa racemose
Ruvini, increase the visibility of this article
If your co-authors confirm their authorship, more researchers will find and read this article on ResearchGate.
Abstract
Sri Lanka is endowed with an abundance of marine resources, yet numerous seaweed species remain underutilized and accumulate as waste along coastal beaches. This represents a missed opportunity to transform marine biomass into valuable resources. The present study was undertaken to evaluate the bioavailability of antioxidants, minerals, and heavy metals in two edible, Sri Lankan seaweeds: Kappaphycus alvarezii and Caulerpa racemose. Seaweed drying at 55 °C and powdered and subjected to the in vitro gastrointestinal digestion, simulating enzymatic breakdown and intestinal absorption using a 12 kDa dialysis membrane. Polyphenol contents were quantified before and after digestion by Folin-Ciocalteu and aluminium chloride colorimetric methods, while antioxidant capacities were evaluated through 2,2-Diphenyl-1-picryl-hyrazyl-hydrate radical scavenging (DPPH) activity, 2,2′ azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging (ABTS) activity and ferric reducing antioxidant power assays (FRAP). Essential minerals (Fe, K, Mg, Al, Zn) and potential heavy metals were analyzed using Inductively Coupled Plasma-Optical Emission spectroscopy. Results revealed significantly higher total phenolic content in bioavailable fractions compared to raw seaweed for both species, while total flavonoid content was undetectable. Notably, bioavailable fractions enhanced antioxidant activity in the ABTS assay, but reduced activity in DPPH radical scavenging compared to raw fractions. C. racemosa showed greater FRAP values in the bioavailable fraction. The bio-accessible
… 
Content uploaded by Mahesh Dhamsara
Author content
Content may be subject to copyright.
Page 1
GreentoGreenInternationalResearchConferenceSRILANKACOUNCILFORAGRICULTURALRESEARCHPOLICYMINISTRYOFAGRICULTURE,LIVESTOCK,LANDSANDIRRIGATIONBOOKOFABSTRACTS
Page 2
Copyright©2025, by the Sri Lanka Council for Agricultural Research PolicyThis book contains the abstracts presented at the Green to Green International ResearchConference (GtoG), held on the 16th December, 2025.Published by: Sri Lanka Council for Agricultural Research PolicyISBN: 978-624-6163-03-7
Page 3
BOOK OF ABSTRACTS, GREEN TO GREEN INTERNATIONAL CONFERENCE16 DECEMBER 2025. ISBN 978-624-6163-03-764 | P a g eBioavailability of Antioxidants, Minerals and Heavy Metals in Two Edible SeaweedSpecies: Kappaphycus alvarezii and Caulerpa racemoseW.G.R. Gangani1, P. Weththasinghe1*, B.C. Jayawardana1, M. Dhamsara1, H.W.S.S. Subhasinghe1,R. Liyanage21Department of Animal Science, Faculty of Agriculture, University of Peradeniya, Sri Lanka2National Institute of Fundamental Studies, Hanthana Road, Kandy, Sri Lanka*pabodhaw@agri.pdn.ac.lkSri Lanka is endowed with an abundance of marine resources, yet numerous seaweed species remainunderutilized and accumulate as waste along coastal beaches. This represents a missed opportunity totransform marine biomass into valuable resources. The present study was undertaken to evaluate thebioavailability of antioxidants, minerals, and heavy metals in two edible, Sri Lankan seaweeds:Kappaphycus alvarezii and Caulerpa racemose. Seaweed drying at 55 °C and powdered and subjectedto the in vitro gastrointestinal digestion, simulating enzymatic breakdown and intestinal absorptionusing a 12 kDa dialysis membrane. Polyphenol contents were quantified before and after digestion byFolin-Ciocalteu and aluminium chloride colorimetric methods, while antioxidant capacities wereevaluated through 2,2-Diphenyl-1-picryl-hyrazyl-hydrate radical scavenging (DPPH) activity, 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging (ABTS) activity and ferricreducing antioxidant power assays (FRAP). Essential minerals (Fe, K, Mg, Al, Zn) and potential heavymetals were analyzed using Inductively Coupled Plasma-Optical Emission spectroscopy. Resultsrevealed significantly higher total phenolic content in bioavailable fractions compared to raw seaweedfor both species, while total flavonoid content was undetectable. Notably, bioavailable fractionsenhanced antioxidant activity in the ABTS assay, but reduced activity in DPPH radical scavengingcompared to raw fractions. C. racemosa showed greater FRAP values in the bioavailable fraction. Thebio-accessible mineral and heavy metal contents were markedly higher in K. alvarezii. These findingsdemonstrate that digestion increases the release and accessibility of polyphenols and minerals inseaweeds, supporting marine biomass recycling as functional ingredients to address micronutrientdeficiencies and oxidative stress-related diseases while promote sustainable resource utilization andreducing coastal waste.Keywords: Antioxidants, Bioavailability, Heavy Metals, In Vitro Digestion, SeaweedAcknowledgement,The authors sincerely thank Mr. Nirooparaj Balachandran, Assistant Director (Coastal–NorthernProvince) at the National Aquaculture Development Authority, Sri Lanka, for his valuable assistancein the collection of seaweed samples.
Similar research
Potential Use of Spike-Topped Apple Snail (Pomacea diffusa) Meal as a Substitute for Fishmeal in Guppy (Poecilia reticulata) Diets
New
Conference Paper
Full-text available
  • Green to Green International Research Conference
Fish meal is a major feed ingredient recognized globally as unsustainable. In addition, identifying underutilized animal protein sources aligns with the principles of the circular economy by promoting resource efficiency and waste reduction for a sustainable future. Thus, the present study investigated the potential of incorporating Invasive Spike-topped apple snail (Pomacea diffusa) meal (SM) as a substitute for fishmeal in guppy (Poecilia reticulata) diets. Four isonitrogenous and isoenergetic diets were formulated: a fishmeal-based control (C) and three treatments with 25%, 50%, and 75% replacement levels of fishmeal using snail meal (25 SM, 50 SM, and 75 SM). The feed-pellet quality was evaluated in terms of pellet expansion and water holding capacity (WHC). Diets containing snail meal exhibited greater pellet expansion, while there was no change in WHC. A total of 360 male golden chest guppy fry (28 days old; initial mean weight 0.09 g) were randomly distributed into 12 outdoor cement tanks and reared for 35 days under natural light conditions. Growth performance, color intensity, and stress tolerance of the guppy as affected by the prepared fish feeds (treatments) were evaluated. In addition, the economic viability of the prepared fish feeds was also evaluated. To evaluate stress tolerance, ten guppies from each replicate were subjected to 30 ppt salinity for two hours, and their survival rate was recorded at the end of the experiment. Feed intake, specific growth rate, and feed conversion ratio showed no significant differences among treatments. Guppies receiving 25 SM and 50 SM diets demonstrated significantly lower (p < 0.05) mean grey values for colour intensity evaluation, indicating improved caudal fin pigmentation. The 75 SM diet resulted in the highest profit index and lowest incidence cost. Diets had no adverse effects on survival during salinity stress. These results indicated that up to 75% of fishmeal can be effectively replaced with P. diffusa meal without compromising growth or stress resilience, while moderate inclusion levels (25–50%) enhanced coloration. Keywords: Feed Pellet Quality, Fishmeal Replacement, Guppy, Snail Meal, Sustainable Feed
Download
Effect of Enzymatic, Fermentation, and Microwave Pre-treatments on Nutrient Composition of Seaweed (Kappaphycus alvarezii)
New
Conference Paper
Full-text available
Seaweed is a sustainable, nutrient-rich source of proteins, carbohydrates, essential fatty acids, and micronutrients. However, its rigid, polysaccharide-rich cell walls limit nutrient bioavailability. Pre-treatment methods can disrupt these cellular structures, enhance nutrient accessibility and support seaweed’s potential as a nutritious ingredient in both animal feed and human food. This study evaluated the effects of different pre treatment techniques, such as enzymatic hydrolysis, yeast fermentation and microwave heating on the proximate composition of Kappaphycus alvarezii. Seaweed samples collected from Jaffna, Sri Lanka were dried, powdered and subjected to one of the six treatments: enzymatic treatment with Allzyme® at 1.5% or 2% (w/w), fermentation with Saccharomyces cerevisiae at 10% or 15% (v/v), or microwave heating at 800 W for 2 or 3 min. Allzyme® contained protease, phytase, cellulose, beta glucanase, amylase and xylanase enzymes. An untreated, sample served as the control. Proximate composition: moisture, crude protein, crude fat, crude fiber, ash, and nitrogen-free extract (NFE), was assessed using AOAC methods. Pre-treatments significantly (p < 0.05) affected seaweed’s nutrient profile. Enzyme treatment (1.5%) increased crude protein content of seaweed from 5.9% to 9.4%, while 10% fermentation yielded the highest protein content (10.0%). Fermentation at 10% and 15% notably reduced fat content (1.0% and 1.8%, respectively), whereas microwave treatment for 2 min produced the highest fat content (3.0%). Crude fiber content decreased with 10% fermentation (7.5%) and 1.5% enzymatic treatment (7.7%) compared to the control (9.8%). The highest NFE value (67.1%) was observed in the 2% enzyme-treated group, indicating enhanced carbohydrate content. Ash content remained relatively unchanged (16.7–17.8%) among the pre-treatment methods. These results demonstrate that enzymatic, microwave, and fermentation pre-treatments enhance the nutritional value and potential bioavailability of seaweed, supporting its use as a functional ingredient in food and feed formulations.
Download
Fatty Acid Profile and Performance of Black Soldier Fly (Hermetia illucens) Larvae Fed Raw and Pre-treated Seaweeds
New
Conference Paper
Full-text available
  • Proceedings of Peradeniya University International Research Symposium and Exposition 2025
Black soldier fly larvae (BSFL; Hermetia illucens) is a sustainable feed source, but their low omega-3 content limits nutritional value. However, this can be improved by rearing them on omega-3-rich substrates such as seaweed. This study evaluated BSFL’s performance and ability to bioaccumulate omega-3 from three seaweed species: Kappaphycus alvarezii, Gracilaria salicornia, and Sargassum wightii. It also examined the dietary effect of different pre-treatments of K. alvarezii on larval omeg-3 enrichment and performance. Two feeding experiments were conducted. In Experiment I, 5-day-old BSFL were reared for 14 days on eight substrates: 100% poultry manure (control), four with 12% of either fish offal or a single seaweed species, and three combining 6% fish offal with 6% seaweed. In Experiment II, 6-day-old BSFL were fed for 14 days on eight substrates: one with 100% poultry manure, one with 67% untreated K. alvarezii, and six with 67% K. alvarezii subjected to pre-treatments (enzyme: Allzyme® at 1.5% or 2%; fermentation: Saccharomyces cerevisiae at 10% or 15%; microwave: 800 W for 2 or 3 min). Experiment I showed that fish offal, whether used alone or in combination with seaweeds, enhanced the omega-3 fatty acid content in BSFL (p < 0.05). Fish offal also improved performance metrics, including feed conversion efficiency, waste reduction, and larval weight gain (p < 0.05). Among the tested seaweeds, only K. alvarezii increased omega-3 levels when used alone, though this came at the cost of reduced larval performance (p < 0.05). Experiment II demonstrated that pre-treatment of K. alvarezii enhanced larval omega-3 content, compared to untreated seaweed (p < 0.05). While both untreated and pre-treated K. alvarezii generally reduced larval performance (p < 0.05), substrates containing pre-treated seaweed showed numerical improvements in growth and efficiency metrics compared to untreated seaweed. These findings highlight the potential of pre-treated seaweed substrates to enrich BSFL with omega-3 fatty acids, offering a promising strategy to improve the nutritional value of insect-based feeds.
Fatty Acid Profile and Growth Performance of Black Soldier Fly Larvae (Hermetia illucens) Grown on Pre-Treated Seaweed
Conference Paper
Full-text available
Despite being a promising feed source for animals, black soldier fly larvae (Hermetia illucens; BSFL) are poor in omega-3 contents. Omega-3 rich substrates can be used to improve the omega-3 content in BSFL, but such substrates also cause poor larval performance. Therefore, this study evaluated the effect of feeding pre-treated seaweed (Kappaphycus alvarezii) on fatty acid profile and performance of BSFL. Eight substrates were prepared using poultry manure as the basal ingredient: a substrate containing 100% poultry manure; a substrate containing 67% untreated seaweed and six substrates containing 67% pre-treated seaweed in six different methods including Allzyme® treated at 1.5% (w/w) and 2% (w/w), fermented with 10% (v/v) and 15% (v/v) Saccharomyces cerevisiae, microwaved at 800 W for 2 and 3 minutes. A total of 6 days-old 9600 BSFL were randomly distributed into 24 plastic containers (400 larvae per container) and fed with one of the eight substrates for 14 days (n=3). At the beginning and end of the experiment, weights of larvae were recorded. Proximate and fatty acid compositions of substrates and BSFL were measured. Inclusion of both untreated and pre-treated seaweed in substrates enriched omega-3 in BSFL. The highest (p<0.05) EPA and DHA contents were observed in BSFL fed seaweed microwaved for 2 minutes and untreated seaweed, respectively. Pre-treated seaweed except enzyme-treated seaweed at 2%, increased (p<0.05) EPA contents in BSFL than untreated treatment. The BSFL fed seaweed showed lower (p<0.05) body weight gain, bioconversion efficiency, nitrogen conversion efficiency than those fed 100% poultry manure. However, in comparison with pretreated seaweed, enzyme-treated seaweed at 2% caused higher (p<0.05) body weight gain compare to the microwave 3 minutes while other performance were same. In conclusion, pre-treatment of K. alvarezii with enzymes, fermentation and microwave can increase the capacity of seaweeds to increase EPA content in BSFL without compromising the performance. Keywords: Black soldier fly larvae, Larval performance, Omega-3 enrichment, Pre treatment, Seaweed
Spike-Topped Apple Snail (Pomacea diffusa) Meal as an Alternative to Fishmeal in Guppy (Poecilia reticulata) Diets
Conference Paper
Full-text available
  • Faculty of Agriculture Undergraduate Research Symposium 2024 (FAuRS 2024)
The present study was conducted to evaluate the effect of dietary inclusion of Spiketopped apple snail (Pomacea diffusa) meal (SM) as an alternative to fishmeal on growth performance, pellet quality, colour enhancement, and stress tolerance in guppy (Poecilia reticulata). Four isonitrogenous and isoenergetic experimental diets were formulated: Fishmeal-based control diet (CD), and three diets replacing fishmeal with SM at 25% (25 SM), 50% (50 SM), and 75% (75 SM). A total of 360, 28-days-old golden chest guppy fry with mean initial weight 0.087±0.00g were randomly distributed and reared in 12 outdoor rearing tanks for 35 days under natural photoperiod (n=3). The growth performance and colour intensity of fish were evaluated. The stress tolerance was evaluated by calculating the survival rate of fish after exposing 10 guppies from each replicate to a salinity of 30 ppt for 2 hours. The pellet expansion of feeds containing SM was higher compared to CD. The dietary inclusion of SM did not affect the feed intake, specific growth rate, or feed conversion ratio of guppies. However, regression analysis showed that feed intake and specific growth rate reduced, whereas feed conversion ratio increased with increasing fishmeal replacement levels. The mean grey values of guppyfed 25 SM and 50 SM were significantly (P<0.05) lower, illustrating higher caudal fin colour intensity. Moreover, fish fed with the experimental diets exhibited a comparable survival rate during the stress tolerance test. The present study showed that fishmeal could be replaced by SM up to 75% without compromising growth performance, pellet quality indexes, caudal fin colour intensity and stress tolerance. However, replacing 25% and 50% fishmeal offers the additional benefits with increased caudal fin colour intensity. Keywords: Fishmeal, Golden apple snail, Guppy, Growth performance, Colour intensity
Download