Biodiesel fuel production via transesterification of oils using lipase biocatalyst

Biodiesel has gained widespread importance in recent years as an alternative, renewable liquid transportation fuel. It is derived from natural triglycerides in the presence of an alcohol and an alkali catalyst via a transesterification reaction. To date, transesterification based on the use of chemical catalysts has been predominant for biodiesel production at the industrial scale due to its high conversion efficiency at reasonable cost. Recently, biocatalytic transesterification has received considerable attention due to its favorable conversion rate and relatively simple downstream processing demands for the recovery of by-products and purification of biodiesel. Biocatalysis of the transesterification reaction using commercially purified lipase represents a major cost constraint. However, more cost-effective techniques based on the immobilization of both extracellular and intracellular lipases on support materials facilitate the reusability of the catalyst. Other variables, including the presence of alcohol, glycerol and the activity of water can profoundly affect lipase activity and stability during the reaction. This review evaluates the current status for lipase biocatalyst-mediated production of biodiesel, and identifies the key parameters affecting lipase activity and stability. Pioneer studies on reactor-based lipase conversion of triglycerides are presented.     

Sperm Bind but Do not Unbind from the Fixed Sea Urchin Egg

In S. purpuratus sperm remained bound to aldehyde-fixed eggs and did not exhibit a detachment phase. Sperm bound in high numbers and the binding curve was similar to that for unfixed homologous gametes. Binding kinetics were analyzed using sequential still photographs of slightly flattened, fixed eggs under supported coverslips. In this way, a single egg could be observed. Alternatively, sperm remaining in the supernatant over settled eggs were counted at successive time points postmixing using spectrophotometry (340 nm) and hemocytometry. Additionally, aliquots of mixed gametes were fixed at successive time points and the numbers of bound sperm determined microscopically on egg perimeters. The maximum number of sperm bound by 2 min; this number remained at or near maximum for as long as 10 min when the experiments were terminated. When sperm were jelly-reacted before addition to eggs, fewer sperm bound, although binding curves were similar to the above experiments. It appears that the binding efficiency of sperm decreases with time after initiation of the acrosome reaction: (1) fewer prereacted sperm bound; and, (2) sperm did not continue to bind after 2 min even though the egg surface was not saturated. Whether these effects are related to motility or other factors is unclear. Furthermore, the above results indicate the importance of the cortical reaction to sperm unbinding. Such studies enable one to observe sperm behavior while precluding the effects of egg secretion during the initial stages of fertilization.     

Response of Elk to Changes in Plant Production and Nutrition Following Prescribed Burning

Abstract: Researchers have ascribed use of areas by grazers after burning to changes in plant community structure, community composition, nutritional quality, and seasonal availability. Researchers can better evaluate these alternatives if they monitor changes in plant communities following burning concurrently with changes in animal use. We examined responses of elk (Cervus elaphus) to prescribed burning of areas dominated by sagebrush (Artemisia spp.) in south-central Montana, USA, within which we monitored changes in plant production, nutritional quality, and community composition and diversity from 1989 to 1999. Elk increased use of burned sites 1–2 years after burning, then reduced use to levels associated with preburn conditions over the next 3–10 years. Burning transformed low-diversity, sagebrush-dominated communities into relatively high-diversity, grass- and forb-dominated communities that persisted for 10 years, but forage biomass and protein content declined on burned sites after initial short-term increases. Changes in elk use closely tracked changes in production and nutritional quality of plants. Therefore, we concluded that increases in quantity and quality of forage were the primary cause for increased use of burned sites by elk. Managers may observe only short-term responses from elk following burning but can expect longer-term increases in plant diversity and persistence of grass—forb communities on burned sites for >10 years that may be important to elk or other grazing ungulates.     

Intensity of radicle fluorescence as related to the resistance of seedlings of lettuce to the lettuce root aphid and carrot to the carrot fly

A technique is described which indicates by u.v. fluorescence the concentration of caffeoylquinic, chlorogenic and isochlorogenic acids in roots of germinating lettuce and carrot. The surface fluorescence of radicles from lettuce root aphid (Pemphigus bursarius) resistant seedlings was more intense than for susceptible seedlings, attributable to the higher concentration of isochlorogenic acid. In contrast, radicles of carrot seedlings resistant to carrot fly (Psila rosae) were less fluorescent than susceptible seedlings, corresponding to the lower concentration of chlorogenic acid in resistant seedlings. The technique is non-destructive and has been developed to distinguish between cultivars or breeding lines potentially resistant to these insect pests.     

Demography of Bristle-thighed Curlews Numenius tahitiensis wintering on Laysan Island

We studied the nonbreeding ecology of Bristle-thighed Curlews Numenius tahitiensis from 1988 to 1991 on Laysan Island in the Northwestern Hawaiian Islands. Using capture-recapture analysis, we estimated that 300–350 curlews wintered on the island. Annual survival was >85% for adults and 92% for first-year birds. Young birds remained on the island until at least their third calendar year, when some individuals made "exploratory" visits to other islands in the Northwestern chain. Most of the birds marked in their first year migrated north to the breeding grounds when they were 3 years old; several birds remained on the island until they were at least 4 years old. Adults returned to the same discrete home ranges year after year, whereas subadults (which do not migrate) tended to use a greater portion of the island. At least 60% of the subadults marked from 1988 to 1990 returned to the island to winter as adults. Because young curlews arrived after adults and experienced high survivorship while on the island, there did not appear to be intense competition for space at Laysan even though the island is at the northern end of the species' winter range.     

Extracellular invertase from Aspergillus flavus

An extracellular invertase was induced in cultures of Aspergillus flavus Link during growth in liquid medium that contained sucrose as the sole carbon source. Synthesis of this enzyme was repressed by the addition of glucose or fructose to sucrose-metabolizing cells, and was induced in a glucose or fructose-metabolizing culture by the addition of sucrose. A. flavus invertase had a pH optimum of 6.0 and an apparent Km of approximately 133 mM for sucrose. The enzyme required potassium phosphate for maximum activity, optimum concentration being 250 mM. The enzyme was partially purified by ammonium sulphate precipitation followed by dialysis and separated by molecular exclusion into three components with molecular weights ranging from approximately 40,000 to 55,000.     

Physiological Aspects of Zebra Mussel Reproduction: Maturation, Spawning, and Fertilization

SYNOPSIS. The prolific reproductive capabilities of the zebramussel, Dreissena polymorpha, have facilitated the rapid spreadand high densities of this biofouling organism since its accidentalintroduction into North America less than 10 years ago. Researchon its reproductive mechanisms and capabilities may be valuablenot only in predicting its further spread, but also in investigatingbasic mechanisms of reproduction and development and in developingnew strategies to mitigate its impact. Since zebra mussels aredioecious and fertilization occurs externally, coordinated maturation,spawning, and other mechanisms have evolved to increase theprobability of successful fertilization. The zebra mussel undergoesan annual cycle of gonadal growth and gamete maturation, culminatingin one or more spawning events in late spring or early summer.Temperature, rates of temperature change, food availability,and effects of neighboring mussels seem to be critical variablesthat determine reproductive responses. Serotonin is a biogenicamine which is implicated in spawning behavior and can reliablytrigger spawning. Serotonin is present in the gonad in neuralvaricosities that encircle groups of gametes, and specific serotonergicligands can mimic or block spawning caused by serotonin. Infemales, serotonin reinitiates meiosis causing maturation fromprophase I to metaphase I prior to spawning. Spawned oocytescontain substances that are species specific sperm chemoattractants.The sequence of binding, entry, and subsequent nuclear movementshave been observed with fluorescence and scanning microscopy.Despite their negative ecological and economic impacts, zebramussels have also provided a new and easily obtainable resourcefor studies of reproductive mechanisms.