Freeze-dried Biomass Research Articles

Experimental broodstock diets as partial fresh food substitutes in white shrimp Litopenaeus vannamei B.

In the first experiment, conducted in a research facility, Litopenaeus vannamei broodstock were fed either a 100% fresh food control treatment (FRE, consisting of frozen squid, oyster, mussel and enriched Artemia biomass in a 2.3:1.4:1.3:1 dry matter ratio) or one of the two treatments in which 50% [dry matter (DM)] of the fresh food was substituted with experimental artificial diets: a dry diet based on freeze-dried Artemia biomass (ART) and a control dry diet (CON). In the second experiment, conducted in a commercial hatchery, shrimp broodstock were fed either a fresh ration (FRE, consisting of frozen squid, polychaetes and enriched Artemia biomass in a 2.5:1.5:1 DM ratio) or the same experimental artificial diets (ART and CON) replacing 50% of the DM by elimination of polychaetes and Artemia biomass. In experiment 1 treatments CON and ART produced better results (P=0.05) than treatment FRE in terms of spawn performance and egg production per female. In experiment 2 no differences were detected among treatments FRE and CON whereas treatment ART performed better (P=0.05) in terms of spawning, egg production per female and spermatophore quality. Broodstock survival and offspring quality did not differ between treatments in either experiment.

Evaluation of extraction methods for recovery of fatty acids from lipid-producing microheterotrophs

The effect of different extraction techniques on the recovery of fatty acids from freeze-dried biomass of two lipid-producing microheterotrophs was examined. Two procedures were used: the extraction of lipids from biomass followed by transesterification of the fatty acids (extraction-transesterification); and the direct transesterification of biomass to produce fatty acid methyl esters (i.e. without the initial extraction step). Variable factors in the extraction-transesterification experiment were the sequence in which solvents were added to the samples, the relative amount of methanol in the solvent mix, and sonication of biomass while in the solvent mix. Variable factors in the direct transesterification experiment were sample size, and reaction duration. Statistical analysis of data (level of significance P<0.05) showed that: (1) extraction of total fatty acids prior to transesterification was significantly more efficient when solvents were added in the order of increasing polarity; (2) neither sonication nor increasing the proportion of methanol in the extraction solvent significantly affected extraction of fatty acids prior to transesterification; (3) efficiency of direct transesterification of fatty acids increased significantly with reaction time; (4) efficiency of direct transesterification of fatty acids was not significantly affected by sample size; (5) the most efficient method for extraction of fatty acids prior to transesterification yielded significantly less fatty acids than the most effective direct transesterification method. While the study examined only two strains, our results suggest that fatty acid analysis methodology for microheterotrophs under consideration for biotechnological exploitation requires optimisation and validation.

A process for high yield and scaleable recovery of high purity eicosapentaenoic acid esters from microalgae and fish oil.

A low expense process is developed for recovering esterified eicosapentaenoic acid (EPA) from microalgae and fish oil. Over 70% of the EPA content in the esterified crude extract of microalgae were recovered at purities exceeding 90%. The recovery scheme utilizes either wet or freeze-dried algal biomass. The process consists of only three main steps: 1) simultaneous extraction and transesterification of the algal biomass; 2) argentated silica gel column chromatography of the crude extract; and 3) removal of pigments by a second column chromatographic step. Argentated silica gel chromatography recovered about 70% of the EPA ester present in the crude fatty ester mixture of fish oil, but at a reduced purity ( approximately 83% pure) compared to the microalgal derived EPA. The optimal loading of the fatty ester mixture on the chromatographic support was about 3% (w/w) but loadings up to 4% did not affect the resolution significantly. The process was scaled up by a factor of nearly 320 by increasing the diameter of the chromatography columns. The elution velocity remained constant. Compared to the green alga Monodus subterraneus, the diatom Phaeodactylum tricornutum had important advantages as a potential commercial producer of EPA. For a microalgal EPA process to be competitive with fish oil derived EPA, P. tricornutum biomass (2.5% w/w EPA) needs to be obtained at less than $4/kg. If the EPA content in the alga are increased to 3.5%, the biomass may command a somewhat higher price. The quality of microalgal EPA compares favorably with that of the fish oil product. Compared to free fatty acid, EPA ester is more stable in storage. Shelf-life is extended by storing in hexane. The silver contamination in the final purified EPA was negligibly small (<210 ppb).

Binding of hard and soft metal ions to Rhizopus arrhizus biomass

Abstract The greater the covalent index value of a metal ion, the greater its potential to form covalent bonds with biological ligands. In this study, freeze-dried Rhizopus arrhizus biomass was tested for its potential to adsorb the hard metal ion Sr 2+ and the borderline metal ions Mn 2+ , Zn 2+ , Cd 2+ , Cu 2+ , and Pb 2+ from aqueous solutions. Equilibrium metal uptake values increased in the order: Sr 2+ 2+ 2+ 2+ 2+ 2+ , and were positively correlated with the covalent index of the metal ions. Equilibrium was rapid and 95% complete within 5 min of contacting the metal ions with the biomass. The potential of the test ions to displace preloaded borderline metals ions from the biomass increased with increasing covalent index. In the case where the hard metal ion Sr 2+ was preloaded, the displacement potential of the borderline test ions decreased with increasing covalent index, except for Pb 2+ , which totally displaced the preloaded Sr 2+ . The potential of a preloaded test ion to inhibit the adsorption of another test ion was also investigated, and similar trends to the displacement studies were observed. As a consequence of test ion adsorption, Ca 2+ and Mg 2+ displacement from the biomass ligands was observed for each test ion and H + displacement was observed for the borderline test ions only. Overall, the hard metal Sr 2+ was found to exhibit ionic binding only, whereas the borderline test ions exhibited a significant degree of covalent binding.

Cadmium adsorption by non-living biomass of the semi-macroscopic brown alga,Ectocarpus siliculosus, grown in axenic mass culture and localisation of the adsorbed Cd by transmission electron microscopy

Non-living, freeze-dried material of the brown algaEctocarpus siliculosus (Phaeophyceae) demonstrated high equilibrium uptake of Cd from aqueous solutions (Fehrmann & Pohl, 1993). The alga was grown in 250-L photobioreactors under various growth conditions (light, salinity and nutrient concentrations) in order to obtain larger quantities of biomass and to improve its Cd adsorption capacity. To derive further knowledge on the biosorbant phenomenon different adsorption parameters such as pH for the sorption process and kinetics of Cd adsorption were tested. The maximum adsorption capacity of the freeze-dried biomass exceeded 41 mg Cd per g biomass. After repeated addition of low Cd concentrations the maximum adsorption capacity was lower (31.4 mg Cd per g biomass). In comparison with other adsorbing materials (activated carbon, silica gel, siliceous earth)E. siliculosus showed significantly higher adsorption capacity. Desorption of deposited Cd with 0.1 M HCl resulted in no changes of the adsorption capacity through five subsequent adsorption-/desorption-cycles. Hence, driedE. siliculosus appears to be an efficient material for the elimination of Cd from industrial waste water.

Adsorption of metal ions by Rhizopus arrhizus biomass: Characterization studies

Freeze-dired, oven-dried, and nonmetabolizing live Rhizopus arrhizus biomass were tested for their capacity to adsorb the test ions, Sr 2+, cd 2+, and Cu 2+, over the pH range 4–6. Metal uptake values for each biomass type were found to increase in the order Cu 2+ > Cd 2+ > Sr 2+. Freeze-dried biomass proved to be the most efficient biomass type for metal adsorption, followed in order by oven-dried and live biomass for Sr 2+ systems, and live and oven-dried biomass for Cd 2+ and Cu 2+ systems. Each test ion displaced constant levels of Ca 2+ and Mg 2+ ions from the three biomass types, indicating that biomass pretreatment had no apparent effect on the ion-exchange capacity of Rhizopus arrhizus. Similarly, the levels of H + displacement resulting from test ion adsorption were unaffected by pretreatment but were found to increase in the order Cu 2+ > Cd 2+ > Sr 2+. Linear reciprocal Langmuir and Scatchard transformation plots reflected the predominantly ion-exchange mechanism of Sr 2+ and Cd 2+ adsorption, and a curved Scatchard transformation plot reflected the more covalent nature of Cu 2+ adsorption.

Cadmium adsorption by the non-living biomass of microalgae grown in axenic mass culture

The freeze-dried (extracted and non-extracted) biomass of 15 microalgal species grown in axenic mass culture and belonging to the Cyanobacteria, Chloro-, Eustigmato-, Phaeo-, Rhodo- and Tribophyceae were investigated for their ability to adsorb cadmium (Cd) ions from aqueous solutions. For comparison, other standard adsorbing materials (activated carbon, silica gel, siliceous earth) were included in the studies. The biomass of 11 microalgae exhibited a higher Cd adsorption than the standard materials. Extraction of the algal biomass increased the Cd adsorption capability of some, but not all microalgae. High Cd adsorption was found inAnabaena lutea, Nodularia harveyana, andNostoc commune (Cyanobacteria),Chlamydomonas sp. (Chlorophyceae),Bumilleriopsis filiformis (Tribophyceae), and inEctocarpus siliculosus, Halopteris scoparia andSpermatochnus paradoxus (Phaeophyceae). The specific surface (m2 cm−3) of the various microalgae was determined by means of laser diffractometry.Anabaena inaequalis andA. lutea (Cyanobacteria) and the Phaeophyceae had especially high Cd adsorption per surface unit. Most of the Cd adsorbed to these various materials could be desorbed subsequently with diluted mineral acid (pH 2).

Isolation, purification, and some physicochemical properties of glucose isomerase from Streptomyces atratus

A highly purified glucose isomerase with a specific activity 23.5 times greater than that of a homogenate of the mycelium has been obtained fromStreptomyces atratus by methods of homogenization from the freeze-dried biomass, heat treatment (70°C, 10 min), ion-exchange chromatography, and gel filtration. The yield of enzyme on the initial biomass was 51.8%. The molecular mass of the enzyme has been determined by various methods as 160 kDa but in the presence of sodium dodecyl sulfate in thin-layer PAG it amounts to 40 kDa.

REMOVAL OF CADMIUM (II) FROM DILUTE AQUEOUS SOLUTIONS BY FUNGAL BIOMASS

ABSTRACT The metal adsorption behavior of nine different species of fungi was investigated. Both batch and kinetic reactors were used to determine the heavy metal, exemplified by cadmium(II), adsorption capacity and the rate of the adsorption reaction. The metal adsorption capacity was assessed at various pH value. Fresh and freeze-dried fungal biomass exhibit similar adsorption behavior. The adsorption capacity of fungal biomass is also compared with other adsorbents such as activated carbon, oxide, soil and hydroxyapatite. The results clearly show that fungal biomass can be as effective as other metal adsorbents.

Mortality of dogs associated with a bloom of the cyanobacteriumNodularia spumigenain the Baltic Sea

Abstract During the normal summer bloom of Nodularia spumigena in August 1982, nine dogs died after having been in contact with the sea water along the Swedish coast of the Baltic Sea. Within one day after exposure the dogs showed the first symptoms and from one to fifteen days after exposure the dogs died, or were sacrificed. In seven out of nine cases the dogs developed jaundice, dehydration and uremia. Toxicity test of Nodularia spumigena revealed 40 lethal mouse units per gram freeze-dried algal biomass.