Valorisation of fish waste biomass through recovery of nutritional lipids and biogas

Commercial fish catch in Eastern Africa is dominated by Nile Perch. Of the fish that is processed for human consumption, 30-40% is wasted. Currently, these wastes are not fully utilized; they are sold off at low price, converted to low valued products or left to decompose leading to environmental pollution and wastage of bioresource. This biomass has however a potential to generate considerable revenue and can be turned into a commercially viable business. It can be used in production of fish oils, bio-energy, proteins and organic fertilizers. Fish oils are a source of n-3 polyunsaturated fatty acids (PUFAs), in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) associated with positive effect on human health. In this study, proteases were used to liberate oil from Nile perch (Lates niloticus) and salmon (Salmon salar) by-products. An oil yield of 11.2% and 15.7% of wet weight was obtained from warm water Nile perch and cold water salmon heads respectively, compared to 13.8% and 17.6% respectively, using solvents. Addition of water during the enzymatic hydrolysis decreased the oil yield. The DHA and EPA contents of oil extracted from Nile perch were 9 and 3 mol%, respectively. To further enrich DHA and EPA contents in Nile perch oil, use of lipases from Candida rugosa, Thermomyces lanuginosus and Pseudomanas cepacia were investigated. In the first case, the lipases were used to hydrolyse the natural oil. Non-regiospecific lipase from C. rugosa gave the best combined enrichment of EPA and DHA with EPA and DHA being enriched to 6 and 23 mol%, respectively. On the contrary, lipase from T. lanuginosus enriched DHA to 38 mol% but was ineffective in enriching EPA. Being a 1,3-specific lipase, the level of enrichment attained with T. lanuginous lipase was to a large extent influenced by the positional distribution of fatty acids within the triglyceride molecule. EPA was mainly in sn 1,3 positions while DHA was equally distributed in the 3 positions. To avoid complications associated with non-homogenous distribution of PUFAs in triglyceride molecules, free fatty acids (FFA) or fatty acid ethyl esters (FA-EE) derived from the natural oil were used as substrates in another study. In this case, lipase from T. lanuginosus was able to enrich both DHA and EPA. Evaluated lipases showed lowest specificity to EPA and DHA when present as ethyl esters and better recoveries of EPA and DHA were achieved when they were present as ethyl esters than when present as FFA or in glycerides. Both esterification of FFA and hydrolysis of FA-EE were more effective at enriching PUFAs than hydrolysis of the natural oil. In an attempt to add more value to fish oil, PUFA concentrate obtained from salmon heads by urea fractionation was used to lipophilize hydrophilic phenolic derivatives (vanillyl alcohol or rutin) which are natural antioxidants. Lipase from Candida antarctica was used to catalyse the esterification reaction. The synthesized lipophilic derivatives showed antioxidant activities with rutin esters showing more activity in the 2, 2-Diphenyl-1-Picrylhydrazyl (DPPH) radical assay than the vanillyl esters and on the contrary in the lipophilic medium, the vanillyl esters were found to be superior to the rutin esters. In bulk oil system, the antioxidant activities of rutin and vanillyl derivatives was lower than that of BHT and α-tocopherol but in emulsion, they showed better activity than α-tocopherol. The PUFA-phenolic molecules carry combined health beneficial properties associated with PUFAs and phenolics. In addition, the PUFAs are protected against oxidation by the phenolic moiety while PUFA makes the antioxidant more lipophilic which may enhance its function in lipid systems. To make maximum utilisation of the fish by-products, the insoluble fraction that remained after oil extraction was used for biogas production through anaerobic digestion. Methane yields before and after oil extractions were 828 and 742 m3 CH4/ton of volatile solids (VS) added, respectively. Despite the high methane yields, fish sludge/fish waste cannot be digested alone in a continuous anaerobic digester due to high content of proteins, lipids and light metals (sodium, potassium and calcium) that are inhibitory to methanogenesis. Co-digestion of the sludge with residues from crop cultivation was thus evaluated. Methane yields were 531 and 403 m3 CH4/ton of VS added when the ratio of Jerusalem artichoke residues: sludge was 1:1 or 3:1, respectively while that of JA alone was 283 m3 CH4/ton of VS. In conclusion, enzyme technology represents valuable tools that can be used in fish processing industries to convert fish waste into products with a higher market value. The use of proteases for the hydrolysis of the by-products results in maximum utilisation of the by-products since the intermediate hydrolysis products can be processed further for valorisation. Lipid fraction can be used for recovery of omega-3 fatty acids and biodiesel. The soluble protein fraction has several applications e.g. in food industries or in microbiological media and the sludge fraction can be used in anaerobic digestion for biogas production. Due to its high protein content, sludge fraction can also be used as animal feed or as biofertilizer due to high content of plant nutrients such as nitrogen, phosphorous and potassium

Characterization of Eggshells Nanocatalyst: Synthesized by Bottom-Up Technology

The sol-gel technique was used to prepare the nanocatalyst from waste egg shells for the production of yellow oleander biodiesel. In this study, the physicochemical and catalytic properties of the nanocatalysts were investigated using: X-ray fluorescence spectrometry (XRF), transmission electron microscopy (TEM), the Barrett-Joyner-Halenda (BJH) model to quantify the pore structure of the samples, and Brunauer-Emmett-Teller (BET) to calculate the exact surface area were the techniques used. The results of the EDX, and XRF analysis showed that the synthesized nanocatalyst was majorly CaO. At 90.46 ± 1.73%, this was higher than the control for incinerated eggshells. From TEM images the particles were spherical in shape with particle sizes ranging from ≈ 7 to 41 nm. BET analysis results indicated that the nanocatalyst was mesoporous with surface area, average pore diameter, and pore volume was; 5.54 ± 0.48 m2/g, 18.57 ± 2.16 nm, and ≈ 0.016 ± 0.0 – 0.017 ± 0.0 cm³/g, respectively. The surface area to volume ratios were 3.27 ± 108 m-1, 2.52 ± 108, and 1.95 ± 108 m-1, respectively. Incinerated eggshells highest followed the synthesized nanocatalyst and CaO, respectively. The synthesized eggshell nanocatalyst was found to be a potential nanocatalyst

Characterization of Eggshells Nanocatalyst: Synthesized by Bottom-Up Technology

The sol-gel technique was used to prepare the nanocatalyst from waste egg shells for the production of yellow oleander biodiesel. In this study, the physicochemical and catalytic properties of the nanocatalysts were investigated using: X-ray fluorescence spectrometry (XRF), transmission electron microscopy (TEM), the Barrett-Joyner-Halenda (BJH) model to quantify the pore structure of the samples, and Brunauer-Emmett-Teller (BET) to calculate the exact surface area were the techniques used. The results of the EDX, and XRF analysis showed that the synthesized nanocatalyst was majorly CaO. At 90.46 ± 1.73%, this was higher than the control for incinerated eggshells. From TEM images the particles were spherical in shape with particle sizes ranging from ≈ 7 to 41 nm. BET analysis results indicated that the nanocatalyst was mesoporous with surface area, average pore diameter, and pore volume was; 5.54 ± 0.48 m2/g, 18.57 ± 2.16 nm, and ≈ 0.016 ± 0.0 – 0.017 ± 0.0 cm³/g, respectively. The surface area to volume ratios were 3.27 ± 108 m-1, 2.52 ± 108, and 1.95 ± 108 m-1, respectively. Incinerated eggshells highest followed the synthesized nanocatalyst and CaO, respectively. The synthesized eggshell nanocatalyst was found to be a potential nanocatalyst

Strategies for the enzymatic enrichment of PUFA from fish oil

A journal Article by Dr. Betty Mbatia, a Faculty in the School of PharmacyPUFA from oil extracted from Nile perch viscera were enriched by selective enzymatic esterification of the free fatty acids (FFA) or by hydrolysis of ethyl esters of the fatty acids from the oil (FA-EE). Quantitative analysis was performed using RP-HPLC coupled to an evaporative light scattering detector (RP-HPLC-ELSD). The lipase from Thermomyces lanuginosus discriminated against docosahexaenoic acid (DHA) most, resulting in the highest DHA/DHA-EE enrichment while lipase from Pseudomonas cepacia discriminated against eicosapentaenoic acid (EPA) most, resulting in the highest EPA/EPA-EE enrichment. The lipases discriminated between DHA and EPA with a higher selectivity when present as ethyl esters (EE) than when in FFA form. Thus when DHA/EPA were enriched to the same level during esterification and hydrolysis reactions, the DHA-EE/EPA-EE recoveries were higher than those of DHA/EPA-FFA. In reactions catalysed by lipase from T. lanuginosus, at 26 mol% DHA/DHA-EE, DHA recovery was 76% while that of DHA-EE was 84%. In reactions catalysed by lipase from P. cepacia, at 11 mol% EPA/EPA-EE, EPA recovery was 79% while that of EPA-EE was 92%. Both esterification of FFA and hydrolysis of FA-EE were more effective for enriching PUFA compared to hydrolysis of the natural oil and are thus attractive process alternatives for the production of products highly enriched in DHA and/or EPA. When there is only one fatty acid residue in each substrate molecule, the full fatty acid selectivity of the lipase can be expressed, which is not the case with triglycerides as substrates

Improved utilization of fish waste by anaerobic digestion following omega-3 fatty acids extraction.

Fish waste is a potentially valuable resource from which high-value products can be obtained. Anaerobic digestion of the original fish waste and the fish sludge remaining after enzymatic pre-treatment to extract fish oil and fish protein hydrolysate was evaluated regarding the potential for methane production. The results showed high biodegradability of both fish sludge and fish waste, giving specific methane yields of 742 and 828 m(3)CH(4)/tons VS added, respectively. However, chemical analysis showed high concentrations of light metals which, together with high fat and protein contents, could be inhibitory to methanogenic bacteria. The feasibility of co-digesting the fish sludge with a carbohydrate-rich residue from crop production was thus investigated, and a full-scale process outlined for converting odorous fish waste to useful products

Fabrication of Nanostructured Polyamic Acid Membranes for Antimicrobially Enhanced Water Purification

Water scarcity and quality challenges facing the world can be alleviated by Point-of-Use filtration devices (POU). The use of filtration membranes in POU devices has been limited largely because of membrane fouling, which occurs when suspended solids, microbes, and organic materials are deposited on the surface of filtration membranes significantly decreasing the membrane lifespan, thereby increasing operation costs. There is need therefore to develop filtration membranes that are devoid of these challenges. In this work, nanotechnology was used to fabricate nanostructured polyamic acid (nPAA) membranes, which can be used for microbial decontamination of water. The PAA was used as support and reducing agent to introduce silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) with antimicrobial properties. The nPAA membranes were fabricated via thermal and wet phase inversion technique and then tested against Escherichia coli and Staphylococcus aureus following standard tests. The resulting nanoparticles exhibited excellent dispersibility and stability as indicated by the color change of the solution and increments of optical density at 415 nm for AgNPs and 520 nm for AuNPs. The wet phase inversion process used produced highly porous, strong, and flexible nPAA membranes, which showed well-dispersed spherical AuNPs and AgNPs whose rough average size was found to be 35 nm and 25 nm, respectively. The AgNPs demonstrated inhibition for both gram positive E. coli and gram negative S. aureus, with a better inhibitory activity against S. aureus. A synergistic enhancement of AgNPs antimicrobial activity upon AuNPs addition was demonstrated. The nPAA membranes can thus be used to remove microbials from water and can hence be used in water purification

Strategies for the enzymatic enrichment of PUFA from fish oil

PUFA from oil extracted from Nile perch viscera were enriched by selective enzymatic esterification of the free fatty acids (FFA) or by hydrolysis of ethyl esters of the fatty acids from the oil (FA-EE). Quantitative analysis was performed using RP-HPLC coupled to an evaporative light scattering detector (RP-HPLC-ELSD). The lipase from Thermomyces lanuginosus discriminated against docosahexaenoic acid (DHA) most, resulting in the highest DHA/DHA-EE enrichment while lipase from Pseudomonas cepacia discriminated against eicosapentaenoic acid (EPA) most, resulting in the highest EPA/EPA-EE enrichment. The lipases discriminated between DHA and EPA with a higher selectivity when present as ethyl esters (EE) than when in FFA form. Thus when DHA/EPA were enriched to the same level during esterification and hydrolysis reactions, the DHA-EE/EPA-EE recoveries were higher than those of DHA/EPA-FFA. In reactions catalysed by lipase from T. lanuginosus, at 26 mol% DHA/DHA-EE, DHA recovery was 76% while that of DHA-EE was 84%. In reactions catalysed by lipase from P. cepacia, at 11 mol% EPA/EPA-EE, EPA recovery was 79% while that of EPA-EE was 92%. Both esterification of FFA and hydrolysis of FA-EE were more effective for enriching PUFA compared to hydrolysis of the natural oil and are thus attractive process alternatives for the production of products highly enriched in DHA and/or EPA. When there is only one fatty acid residue in each substrate molecule, the full fatty acid selectivity of the lipase can be expressed, which is not the case with triglycerides as substrates

Enzymatic enrichment of omega-3 polyunsaturated fatty acids in Nile perch (Lates niloticus) viscera oil

Oil was extracted from fatty material obtained from Nile perch viscera using the protease Protex 30L. Enrichment of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the glyceride fraction was carried out by hydrolysis of extracted oils with lipases from Candida rugosa, Thermomyces lanuginosus and Pseudomonas cepacia. The unusual fatty acid distribution of the oil influenced the apparent lipase specificity to a large extent. In the unhydrolysed oil, only 16% of EPA was in sn-2 position while 51% of palmitic acid was located in this position of the triacylglycerol (TAG) molecules. Non-regioselective lipase from C. rugosa was the most effective in combined enrichment of both EPA and DHA. This was partly because it was able to hydrolyse off palmitic acid from the sn-2 position, which 1-, 3-specific lipases were unable to do. Hydrolysis with C. rugosa lipase enriched EPA from 3 to 6 mol% and DHA from 9 to 23 mol%, with recoveries of 42 and 55%, respectively. The 1-, 3-specific lipase from T. lanuginosus was ineffective in enriching EPA, but gave best DHA enrichment, 38 mol% with a recovery of 39%. DHA was rather equally distributed in sn-1, - 2 and - 3 positions of TAG. The results show that both the fatty acid specificity and regiospecificity of the lipase as well as the fatty acid distribution of the oil should be considered when choosing the strategy for fatty acid enrichment

Enzymatic oil extraction and positional analysis of omega-3 fatty acids in Nile perch and salmon heads

The use of commercial proteases, bromelain and Protex 30L for oil extraction/recovery of polyunsaturated fatty acids (PUFA) from Nile perch and salmon heads was evaluated. Four phases were obtained after hydrolysis, oily phase, emulsion, aqueous phase and sludge. An increase in water content during the hydrolysis resulted in a decrease in oil yield. Maximum oil yield was obtained when hydrolysis was performed with Protex 30L at 55 C, without pH adjustment or water addition. An oil yield of 11.2% and 15.7% of wet weight was obtained from Nile perch and salmon heads, respectively, compared to 13.8% and 17.6%, respectively obtained using solvent extraction. Fatty acid distribution analysis showed 50% of palmitic acid was in sn-2 position in Nile perch triglycerides (TAG), while only 16% of this fatty acid was in sn-2 position in salmon oil TAG. (C) 2010 Elsevier Ltd. All rights reserved

Anti-Oxidative Potential of Honey and Ascorbic Acid in Yoghurt Fortified With Omega-3 Fatty Acids

A Journal Article by Dr. Betty Mbatia, a Lecturer in the Faculty of Pharmacology and Health Sciences at USIU - AfricaProcessing of Nile perch (Lates niloticus), a commercial fish in Eastern Africa; results in omega-3 polyunsaturated fatty acids (PUFA) rich by-products. Oil derived from such by-products can be incorporated in commonly consumed foods; however, these fatty acids are highly susceptible to oxidation. Honey and ascorbic acid are natural anti-oxidants that could play a role in preventing lipid oxidation. In the current study, omega-3 rich oil was extracted from L. niloticus viscera and added to yoghurt samples. The aim of the study was to investigate the biochemical and anti-oxidative parameters in honey and lemon juice and use them as antioxidants in the fortified yoghurt samples. Stability of the fortified yoghurt was monitored over one month storage period. Ascorbic acid Equivalent Antioxidant Capacity (AEAC) of lemon juice and honey were 312 ± 2.34 and 197 ± 3.65 mg/L, respectively. The DPPH radical scavenging activity showed that honey (86.16± 1.43%) tended to be highly active in the reaction with DPPH compared to lemon juice (71.29± 3.52%).After four weeks of storage, the peroxide value (PV), anisidine value (AV) and (free fatty acid) (FFA) contents were within the acceptable range with the honey fortified sample being most stable. The ascorbic acid content was highest in lemon juice fortified samples (30 mg/100g) while in honey fortified samples were below 1mg/100g. The pH in all the samples decreased slightly over time. Honey and lemon juice are therefore good natural anti-oxidants and their anti-oxidative potential can be utilized in the prevention of lipid oxidation in omega-3 fortified yoghurts