To date, we have generated revenue from research collaborations, government grants and enzyme product sales. Celanese Ltd. Our current government grants are from the National Institute of General Medical Sciences, the National Cancer Institute and the National Institute of Environmental Health Sciences. Our enzyme product sales through September 2000 are comprised of research kits and Pyrolase 160 and 200, enzymes used in oil and gas recovery. We have dedicated substantial resources to the development of our proprietary technologies, which include capabilities for sample collection from the world's microbial populations, generation of environmental gene libraries, screening of these libraries using ultra-high throughput methods capable of analyzing more than a billion genes per day and optimization employing our gene evolution technologies. This increase was primarily attributable to the addition of new strategic collaborations, which include exclusivity fees, technology access and development fees and research funding.
Research funding is recognized as revenue when the services are rendered.
Revenue from exclusivity, technology access and development fees is recognized over the term of the strategic collaboration. Revenue from milestone payments is recognized when the milestone is achieved. Our strategic partners often pay us before we recognize the revenue, and these payments are deferred until earned. We have incurred substantial operating losses since our inception. We expect to incur additional operating losses over the next few years as we continue to develop our technologies and fund internal product research and development.