Thursday, 21 September 2017

 

Researchers at PennState's College of Agricultural Sciences have developed a new approach to more efficiently convert potato waste into ethanol, as Pennsylvania has more than two dozen companies manufacturing potato chips. 

This process may lead to reduced production costs for biofuel in the future and add extra value for chip makers.

Using potato mash made from the peelings and potato residuals from a Pennsylvania food-processor, researchers triggered simultaneous saccharification — the process of breaking down the complex carbohydrate starch into simple sugars — and fermentation — the process in which sugars are converted to ethanol by yeasts or other microorganisms in bioreactors.

The simultaneous nature of the process was innovative, according to researcher Ali Demirci, professor of agricultural and biological engineering. The addition to the bioreactor of mold and yeast — Aspergillus niger and Saccharomyces cerevisiae, respectively — catalyzed the conversion of potato waste to bioethanol.

The bioreactor had plastic composite supports to encourage and enhance biofilm formation and to increase the microbial population. Biofilms are a natural way of immobilizing microbial cells on a solid support material. In a biofilm environment, microbial cells are abundant and more resistant to environmental stress causing higher productivities. In this application, these benefits were especially important because mold enzyme activity required higher temperature and the yeast had to tolerate this.

Researchers evaluated the effects of temperature, pH and aeration rates in biofilm reactors, and the optimal conditions were found to be 95 degrees Fahrenheit and a pH of 5.8 with no aeration. After 72 hours, the researchers achieved the maximum ethanol concentration of 37.93 grams per liter. The yield was 0.41 grams or ethanol per gram of starch.

"These results are promising, because the co-culture biofilm reactor provided similar ethanol production — 37.93 grams per leader — compared to the conventional ethanol production — 37.05 grams per liter — which required pre-treatment with added commercial enzymes at a higher temperature," Demirci explained. "Therefore, eliminating the externally added enzyme and energy costs will certainly reduce the cost of bioethanol production."

"This research is of great interest to Keystone Potato Products in Hegins, Pennsylvania, a subsidiary of Sterman Masser Inc.," said Demirci. "The company is paying attention to this project, hoping this novel approach may help it add more value to its waste potato mash. Industrial food wastes are potentially a great substrate in production of value-added products to reduce the cost, while managing the waste economically and environmentally."

Also contributing to the research was John Cantolina in the Microscopy and Cytometry Facility at the Huck Institutes of the Life Sciences, PennState.

The Turkish Ministry of Education, by providing a scholarship to Izmirlioglu and the Pennsylvania Agricultural Experiment Station supported this work.

Photo caption:  Researcher Ali Demirci adjusts a bioreactor in which potato waste is being used to produce bioethanol with a novel process that simultaneously employs mold and yeast to convert starch to sugar and sugar to ethanol.

Related articles: 

Protein Recovery from Potato Processing Stream Waste Using Membrane Technology 

Tesco Brings Together Potato Suppliers to Reduce Food Waste 

TOMRA Sorting Food: steam peeling can reduce the waste within the potato industry

Government aid to help reduce waste at Canadian McCain facility 

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