Agar Production and Quality from Gracilaria sp. Strain G —16: Effects of Environmental Factors

Abstract

A strain of Gracilaria sp., G-16, which produces an agar with high gel strength was grown under controlled culture conditions at 3 different temperatures, 2 light quantum fluxes, 2 salinities, and under N enrichment and starvation. Best productivity occurred at 24 °C, followed by 32 °C, then 15°C. Higher light quantum fluxes and nitrogen enrichment also contributed to greater productivities. Salinity changes of 17%o versus 33%o showed minimal effect on productivity. Slight salinity effects occurred when other culture factors contributed to reduced growth. Agar content was typically greater in plants grown at 17%o than 33%o, and was generally lower in plants grown at 32 °C than 24 or 15 °C. There was some effect of thallus N levels on agar content. Agar gel strength was greater in the N enrichment treatments, and was also affected by both temperature and salinity. The highest agar gel strength was found in the 32 °C, N enriched, 33%o treatments. Lower salinities of 17%o led to reductions in agar gel strength, but more significantly, the N enrichment effect on increased gel strength disappeared.

Standing Stock, Agar Yield and Properties of <i>Gracilaria salicornia</i> Harvested along the Tanzanian Coast

“…Furthermore, Hoyle (1978) found that low agar yields in the winter were associated with higher total thallus nitrogen content in two Gracilaria species. Other studies supporting the observations are those of DeBoer (1979); Lahaye & Yaphe (1988); Bird (1988) and Oyieke (1993).…”

“…Other factors which influence agar quality include nutrient status of the media in which algae grow (Bird, 1988;Chiles et al, 1989), age (Lignell & Pedersén, 1989) and reproductive status of the plants (Givernaud et al, 1999), molecular weight of the polymer (McKinnon et al, 1969), concentration of cations such as K + (McKinnon, 1973), methoxyl content (Arnott et al, 1974a), pyruvic acid (Arnott et al, 1974b), the concentration of alkali for seaweed treatment prior to extraction.…”

Influence of nitrogen availability on agar-polysaccharides fromGracilaria verrucosa strain G-16: structural analysis by NMR spectroscopy

“…In this study, G. verrucosa strain G-16 was grown under controlled culture conditions at two different salinities, two light quantum fluxes, three temperatures and under nitrogen enriched or limited conditions. Subsequent analyses revealed that the most marked differences in agar properties were those between the nitrogen enriched and deficient cultures grown at 32 C and 33% (Bird, 1988;Bird et al, in press). Agar from the nitrogen enriched culture had a higher measurable gel strength (1083 g cm-2) and a lower gelling temperature (42 °C ) relative to agar obtained from nitrogen limited conditions (gel strength of 525 g cm-2, gelling temperature of 47 °C ).…”

“…Although the basis of seasonal variations remains unclear, culture studies indicate that nutritional status (Bird et al, 1981;Craigie et al, 1984) plays a significant role. Culture studies with Gracilaria verrucosa Papenfuss strain G-16 also indicate that nitrogen availability, temperature, and salinity significantly affect the physical properties of agar gels (Bird, 1988;Daugherty & Bird, in press).…”

Agar Analysis, nuclear genome quantification and characterization of four agarophytes (Gracilaria) from the Mexican Gulf Coast

“…The three species with the lowest agar yields were collected during July, when temperatures can exceed 30 0 C. Gracilaria caudata was collected in December, when temperatures are much cooler. Bird (1988) (Table 5), but they still are low when compared with commercial agarophytes (Bird & Hinson, 1992). Previous comparisons of genome organization and complexity data with information for gel quality suggested a possible correlation between genome profiles and synthesis of commercial-grade agars in species of the Gracilariales (Dutcher et al, 1990;Kapraun et al, 1993b).…”