This publication is the seventh of a series of seven supplementary investigative materials for use in secondary science classes providing up-to-date research-related investigations. This unit is structured for grades 7 through 10. It is concerned with the roles of fermentation processes in the agriculture and food industry. The guide enables students to study the effect of temperature on the rate of fermentation by yeasts. The first part of this guide provides the teacher with: (1) materials needed; (2) supplementary information; (3) preparation of sugar solution and yeast suspension; and (4) suggested readings. The second part provides students with background information and one laboratory investigation - fermentation: activities of a fabulous fungus. The investigation consists of: (1) materials needed for a four-student team; (2) procedures; (3) questions for thought; (4) extending the investigation; and (5) suggested readings. (HM)