Team:Worldshaper-Nanjing/Description
Inspiration
The inspiration for our project came from the recent reinforcements in waste sorting. With trash classification being the top hits and kitchen waste being the most troublesome to deal with, our team wanted to find a way to use bio-synthetics to turn kitchen waste into something usable. However, after researching kitchen waste and current ways of dealing with them, our team found that kitchen waste is incredibly diverse, including solids like bones, shells, meats, leaves, rice, etc. and liquids like soups and lipids. It would be almost impossible for us to find a way suitable for all the contents of kitchen waste and treat them[1]. In order to narrow down our topic, we are honored to invite Dr. Sun to accept our interview who inspired us to pay attention to another type of food waste, stale grain, also then, with the help of Prof. Shen, renaming to the substandard grain in the following articles.
Substandard Grains
Components of Substandard Grains
Current Solutions to Substandard Grains
- Those that meet the standard of feed grain should be used as feed
- Those that meet the standards for industrial grains shall be used as non-edible industrial grains
- If it has no use-value after inspection, compost, incineration, etc. shall be adopted for harmless disposal
Biodiesel
Current Biodiesel Production Routes
- microbial oil route
- microalgae oil route
- plant oil route
Background
Substandard grains refer to raw grains, including corn, rice, wheat, etc. that contain heavy metals, mycotoxins, pesticide residues, and other toxic and harmful substances that do not meet the limit requirements of the national food safety standards[2] . Due to the inadequate demand of the market, inefficient storage, or trade of grains, and inappropriate production and storage, substandard grains problems are inevitably occurring. As learned from the interview with Prof. Shen (see more details on our Human Practices page), China has made a lot of effort in the collection and processing of substandard grains. Moreover, the purchase, storage, and sale of it are directly supervised by the grain department to ensure food security.
The toxins or harmful substances contained, such as aflatoxin, are harmful to humans and animals, can be fatal in severe cases. Thus, substandard crops are unavailable for neither humans nor animals. However, as learned from the results of our Public Survey, 65.76% of the participants are not aware of stale grains (one type of substandard grain) issues before coming across this survey, which tells us that public awareness for substandard grains is relatively low. Still, a amount of 24.3% of participants considered stale grains edible. Coincidentally, in October this year in China, we were sorry to hear about a family food poisoning incident caused by excessive aflatoxin caused by long-term storage. It makes us firmly believe in the necessity and meaning of our project.
As shown in Table 1, gains mainly consists of carbohydrate, protein, fibers, water, and lipids (oil). Among them, the main carbohydrates include starch, soluble sugar, crude fiber, and the amount of starch is the most. For example, the starch in corn is about 62%. Therefore, to deal with the problem of substandard grains, we first need to start with starch.
By consulting the government website and hp interviews, we learned that there are currently three treatment options for substandard grains:
Because we are concerned about the reuse of substandard grains, we will focus on the ways to be used as industrial grains, i.e. used as fermentation for alcohol production.
Industrial alcohol production from substandard crops has been around since the late 20th century and is still in use today. There are different kinds of raw materials for alcohol fermentation, including grains containing sugar, starch, and cellulose.
The basic steps of alcohol production using starch grains include breaking down long starch chains into glucose with high temperature, certain enzymes, and mild acid solution; then ferment with yeasts that produce bio-alcohol. Of course, the grains should first be milled and turned into liquid for the above actions to take place, and a safety precaution to prevent yeast leakage should also be in place[4].
Biodiesel, as one of the major biofuels, has attracted more and more attention recently because of much less Green House Gas (GHG) emissions than that of fossil fuel counterparts on a per unit energy basis. As shown in Figure 2, the estimated GHG emissions reduction is that 49-73% by using biodiesel relative to gasoline on a per MJ energy basis.
Therefore, bioenergy production is a key development project worldwide. However, in China, the production of biofuels is far from meeting the targets set of the "Twelfth Five-Year Plan" and the 2020 goal of the National Development and Reform Commission (2020) (Figure 3). It is mainly due to the limited supply of raw materials and the maintenance of food self-sufficiency[5].
Nowadays, there are mainly three typical routes to produce biodiesel, including(Figure 4):
Plant oil or waste edible oil/fat is still the main source of biodiesel production through enzymatic pathways, but production capacity is limited by uncertain vegetable oil supplementation or inconsistent waste oil/fat quality. Microalgae oils directly from CO2 via a photosynthesis process is also an optional route now but has the limitation of the slow growth of microalgae on carbon dioxide and low light efficiency, high production cost. Meanwhile, many oleaginous microorganisms have been developed to produce lipids via the fatty acid synthesis pathway under aerobic fermentation conditions. Among them, it is suggested that Y. lipolytica, an unconventional dimorphic yeast, is a promising biocatalyst for commercial biodiesel production in the future[7] .
Figure 4 An overview of biodiesel production via three typical routes: (1) microbial oil route; (2) microalgae oil route; and (3) plant oil route[7].
Y. lipolytica is often found in fermented foods, such as cheese and meat, and is a good natural producer of some industrial compounds, including citric acid, erythritol, various proteins and lipids. Y. Lipolytica's metabolism is well suited for fatty acid production and lipid accumulation and is therefore used as a host organism that produces large amounts of lipids[8–11] . As shown in Figure 5, it is can only ultilize various C6 sugars such as glucose, fructose, mannose, and galactose, and thus pre‑treatments and expensive enzymatic are needed, including steaming, ɑ-amylase liquefying, and then acid hydrolysis or glucoamylase treatment, etc.
Figure 5 An overview of metabolic pathways in Y. lipolytica for synthesis of fatty acids from various substrates[7].
Our Project
The goal of our project is to turn substandard crops, mainly inedibel corn that has been stored too long and lost the adequate nutritional value for human ingestion, into biological diesel using genetically engineered Y. Lipolytica--a kind of yeast. We will engineer Y. Lipolytica to produce α-amylase and glucoamylase, two enzymes that break the glycosidic bonds and turn starch into smaller glucose molecules. The starch in grains is broken into glucose, which can then be used as a source of nutrition for the Y. Lipolytica. Y. Lipolytica will then produce bio-fuel through its metabolic pathway. See more detailed design on our Designpage.
References
- HOW IS FOOD WASTE RECYCLED? https://www.recyclenow.com/recycling-knowledge/how-is-it-recycled/food-waste (accessed Jun 30, 2020).
- Notice of Jiangsu Province’s Measures for Disposal of Substandard Grain http://www.jiangsu.gov.cn/art/2018/3/1/art_46144_7498212.html (accessed Oct 21, 2020).
- Nutritional diet query-food database http://db.foodmate.net/yingyang/type_0%3A1%3A85_1.html (accessed Oct 10, 2020).
- Mohanty, S. K.; Swain, M. R. Bioethanol Production From Corn and Wheat: Food, Fuel, and Future. In Bioethanol Production from Food Crops; Elsevier, 2019; pp 45–59. https://doi.org/10.1016/b978-0-12-813766-6.00003-5.
- USDA, （U.S. Department of Agriculture）. China’s 2014 Fuel Ethanol Production Is Forecast to Increase Six Percent [GAIN Report Number: CH1403]; 2014.
- Qin, Z.; Zhuang, Q.; Cai, X.; He, Y.; Huang, Y.; Jiang, D.; Lin, E.; Liu, Y.; Tang, Y.; Wang, M. Q. Biomass and Biofuels in China: Toward Bioenergy Resource Potentials and Their Impacts on the Environment. Renew. Sustain. Energy Rev. 2018, 82 (March), 2387–2400. https://doi.org/10.1016/j.rser.2017.08.073.
- Xie, D. Integrating Cellular and Bioprocess Engineering in the Non-Conventional Yeast Yarrowia Lipolytica for Biodiesel Production: A Review. Front. Bioeng. Biotechnol. 2017, 5 (OCT). https://doi.org/10.3389/fbioe.2017.00065.
- Park, Y. K.; Nicaud, J. M.; Ledesma-Amaro, R. The Engineering Potential of Rhodosporidium Toruloides as a Workhorse for Biotechnological Applications. Trends in Biotechnology. 2018, pp 304–317. https://doi.org/10.1016/j.tibtech.2017.10.013.
- Park, Y. K.; Dulermo, T.; Ledesma-Amaro, R.; Nicaud, J. M. Optimization of Odd Chain Fatty Acid Production by Yarrowia Lipolytica. Biotechnol. Biofuels 2018, 11 (1). https://doi.org/10.1186/s13068-018-1154-4.
- Darvishi, F.; Ariana, M.; Marella, E. R.; Borodina, I. Advances in Synthetic Biology of Oleaginous Yeast Yarrowia Lipolytica for Producing Non-Native Chemicals. Applied Microbiology and Biotechnology. Springer Verlag July 1, 2018, pp 5925–5938. https://doi.org/10.1007/s00253-018-9099-x.
- Friedlander, J.; Tsakraklides, V.; Kamineni, A.; Greenhagen, E. H.; Consiglio, A. L.; MacEwen, K.; Crabtree, D. V.; Afshar, J.; Nugent, R. L.; Hamilton, M. A.; Shaw, A. J.; South, C. R.; Stephanopoulos, G.; Brevnova, E. E. Engineering of a High Lipid Producing Yarrowia Lipolytica Strain. Biotechnol. Biofuels 2016, 9 (1). https://doi.org/10.1186/s13068-016-0492-3.