EFFECTS OF PHOSPHATE AND NITRATE SUPPLY ON PRODUCTIVITY, AGAR CONTENTAND PHYSICAL-PROPERTIES OF AGAR OF GRACILARIA STRAIN G-16S

Citation
Rj. Lewis et Md. Hanisak, EFFECTS OF PHOSPHATE AND NITRATE SUPPLY ON PRODUCTIVITY, AGAR CONTENTAND PHYSICAL-PROPERTIES OF AGAR OF GRACILARIA STRAIN G-16S, Journal of applied phycology, 8(1), 1996, pp. 41-49
Citations number
34
Categorie Soggetti
Biothechnology & Applied Migrobiology","Marine & Freshwater Biology
ISSN journal
09218971
Volume
8
Issue
1
Year of publication
1996
Pages
41 - 49
Database
ISI
SICI code
0921-8971(1996)8:1<41:EOPANS>2.0.ZU;2-1
Abstract
Gracilaria strain G-16S was cultured in various phosphorus (P) supply rates with low or high nitrogen (N) supply to determine the effects of nutrient supply on its productivity, agar content and physical proper ties of the agar. Productivity was reduced after four weeks of growth in zero P supply as plants reached 0.07% P tissue content (critical le vel), with fragmentation of these plants by six weeks (0.05% P; minimu m viable level). Native agar content was higher in low P and high N, o r low N conditions. Agar content appeared to increase with decreasing P under high N supply. This increase was not apparent with alkali trea tment prior to extraction. Agar gel strength was greatly increased by alkali treatment. The highest gel strengths were obtained under high N supply at all P supply rates except zero P, and under low N supply at 12 mu M P week(-1). Native agar gel strengths showed a similar patter n on a lower scale. Melting temperatures were higher in agars with hig her gel strengths. Dynamic gelling temperatures were generally high fo r alkali-treated agar, with agar from plants grown in zero P supply sh owing a slightly elevated gelling temperature. Melting and gelling tem peratures of native agars with the highest gel strengths were in the s ame range as bacteriological agar. These results show that P and N sup ply affects productivity, agar content and agar physical properties, b ut the tradeoffs between a slightly higher agar quantity under nutrien t limitation and higher agar quality under nutrient-replete conditions seem to favor the latter.