2644 - CSUN ScholarWorks - California State University, Northridge

Journal of Student Research Abstracts · 5
Tomasek. The "lamp" is constructed from colorful yeast beads encapsulated in a glass/alginate mixture. When
the beads are placed in an enclosed container or sugar and water, they will slowly rise to the surface of the partially
filled container, pause momentarily, then slowly descend to the bottom. The motion of the beads repeats
until all of the sugar is metabolized by the yeast. The slow, continuous movement of the colored beads is reminiscent
of the 1960's lava lamps. Quantitative measurement of this metabolism is recorded by carbon dioxide
bubble counters (fermenters) placed on top of the containers, usually two-liter plastic bottles. Students were
able to implement the King-Tomasek protocol, construct the "lamp", and measure optimal sugar (sucrose) concentrations.
Sugar concentrations in different containers were "tagged" by different colored yeast beads with
uncolored beads given to the control of no sugar or 0% concentration. Students evaluated carbon dioxide productivity
by (a) maximum bubble count, and (b) longevity of output. Bubble counts were recorded on a daily
basis for a number of days. A 20% (by weight) sugar concentration was found to be optimal by the students
according to productivity criteria. This optimum can serve as a control for further student experimentation on
yeast-sugar (or sweetener) metabolism.
2642
UNDER WHAT CONDITIONS DOES YEAST RESPIRE THE MOST RAPIDLY?
Stephen Herr, and Shirley Deedon (teacher). Valley Presbyterian School, 9200 N. Haksell Ave., North Hills,
CA 91343.
Experiments were developed to determine the optimal conditions for yeast respiration as measured by the
production of carbon dioxide that was collected by water displacement. Flasks containing 2.0 grams of baker's
yeast, Saccharomyces cereviseae, and a constant amount of sucrose, were placed in water baths at different
temperatures from 1 oo to 70° C. It was determined that yeast respired best at approximately 45° C. When the
experiment was repeated at 45° C using sugar concentrations from 0 to 30% (by weight), it was determined
that yeast respired most rapidly in a 24% sucrose solution. Keeping the temperature at 45° C, yeast was put in
24% sugar solutions ranging from pH 1 to 12 and it was found that yeast respired most rapidly at pH 7. It was
determined that the addition of salt reduced the respiration rate when temperature, sugar concentration and pH
were kept constant at optimal values. When Nutra-sweet® was substituted for sucrose the respiration rate
decreased indicating that yeast respires more rapidly in natural sugar. It was concluded that baker's yeast
respires most rapidly at 45° C, in 24% sucrose solution, at a pH of 7, with no additional salt.
2643
CAN COLLEMBOLAS BE LOCATED ON HARTE MIDDLE SCHOOL CAMPUS?
Cindy Martinez, Jose Lopez and Dr. Charles B. Lawrence (teacher). Bret Harte Preparatory Intermediate
School, 9301 Hoover Street, Los Angeles, CA 90044.
Experiments were designed to test the hypothesis that collembolas could be found on Harte M.S. Campus.
Six (6) separate sites were used to collect leaf litter and soil samples. Each site was indicated on the data sheet
and school site maps produced by the class and each site was tested for collembola. The Tullgren funnel and
floating methods were used along with a loop to collect collembola from the collecting jars and place the located
collembola into a culture jar, which was established using activated charcoal and plaster of paris. Two
species of collembola were found at three of the six sites. Entomobryidae were located on two sites both in
leaf litter, neonuridae were located on one site, also in leaf litter. A completed data sheet and site map of all
findings is being kept. Culture jars consisting of collembolas located are being kept, fed household yeast and
watered with a pipette on a daily basis, as culturing is continuous. It is concluded that collembolas can be located
on Harte M.S. Campus.