With the increasing public concern for food safety worldwide, scientists have always been striving to solve dilemmas in food quality control from the root of the problem through cutting-edge technology. In recent year, Chinese people’s food safety concerns focus on “gutter oil”, which is made from discarded cooking oil and kitchen waste. Theoretically, there are many sources to dispose and reuse gutter oil, including manufacturing biodiesel and detergent. However, lack of mature policies of the biodiesel production leads to the low profitability, which further breeds the emergence of the “black market” that sends gutter oil back to the table. To tackle this problem, Worldshaper-Nanjing came up with a new solution: converting gutter oil to γ-linolenic acid, a substance with high economic and nutritional value. To achieve the balance in cost and effectiveness, we consider the interdependence between different stakeholders to release the greatest potential of our approach.
Fig.1 Overview of Human Practice
Integrated Human Practices
In the integrated human practice section, we plan to highlight how the imformation and feedback we got affect our project.
1. In depth background investigation and understanding of oil recovery and regeneration industry
According to the descriptions of city Administration Bureau, oil recycling manufacturers and restaurants, we have a deep understanding of the recycling route of wast edible oil:
Waste oil comes from food waste disposal plants, food factories, restaurants, etc. After being discarded, waste edible oil are collected by the recycling manufacturers without obstacles, because there is a policy that all factories and restaurants must sell the waste oil to the recycling company approved by the government. The regulatory authorities will approve a number of enterprises to collect waste edible oil as much as possible regardless of whether it contains a large amount of impurities and residues. The recovered waste oil is transformed into biodiesel after pretreatment by oil-water separation and filtration.
Therefore, we preliminarily determined the industrial application of our project: the biotransformation system should be designed in the waste oil recovery factory.and the waste oil can be collected in cooperation with the waste oil recovery company, which is helpful to remove a large amount of solid waste residues. The pretreated waste oil enters the "solid-liquid separation system" designed by us for further filtration, and then enters the fermentation step.
Fig.2 The general process of linolenic acid production
2. Improve our biotransformation system step by step
We improved the design of fermentation tank according to the suggestions of team instructors and experts. The first is to ensure all culture parameters of yeast fermentation reaction, including temperature, pH, oxygen, etc. Pre culture of yeast, addition of defoamer and acid-base reagent were also considered into the design.
According to HUST-China's recommendations, we added three types of agitators to the mixing system: the defoaming paddle is located at the liquid surface, and its grid-like shape allow its upper part to collide and stir up the bubbles on the liquid surface and the lower part to destroy the generated bubbles, thus controlling the increase of the foam. The two impellers move the liquid laterally and vertically respectively and so can make the liquid fully stirred in all directions.
According to the suggestion of Dr. Dongsheng Guo, we added a detecting system , a gas distributor, and a water bath heater to the fermentation system. The function of the gas distributor is to blow in sterile air and distribute the air evenly. The function of water bath heater is to maintain the temperature in the fermentor at the most suitable 30 ℃ for yeast. The detecting system is composed of a PH electrode, a dissolved oxygen electrode, a temperature electrode, and a central control center, which further ensures the steady state of fermentation environment.
The actual production process of the oil company gave us further inspiration. Every production link of a real factory needs to control costs, including the purchase of raw materials, the circulation of energy and materials, and the balanced use of personnel and equipments. Therefore, when designing thermostat water bath system and sterile ventilation system, we refer to the current design with high efficiency, low cost and low energy consumption.
Fig.3 The whole hardware device system
3. Clear goals of science communication
The results of the public survey show that most people don’t know the types of harmful substances in gutter oil and the actual wide use of gutter oil. Although people show strong interest in biotransformation and synthetic biology, in fact, they do not understand the technology and application in this field.This makes us realize that we should focus on incorporating scientific knowledge into our public communications.
1. Understand current situation
In order to effectively understand the reality of gutter oil recycling in China, we investigated every step of waste oil treatment, including discarding, transportation and recycling.
In our region, the Public Security Bureau, Food and Market Supervision and Management Bureau, and other related institutions collectively regulate gutter oil at the source to ensure the discarded oil is sent to the appropriate recycling company. The next stage of processing raw oil is overseen by the City Administration Bureau.
City Administration Bureau
---Mr. Qiuyang Sun, Nanjing City Administration Bureau
We luckily got into contact with Mr. Qiuyang Sun in the Environment and Hygiene Department in Nanjing City Administration Bureau. Mr. Sun said the food safety office has attached great importance to gutter oil problem for long. The environmental health department calls gutter oil “waste edible oil”, and there are three levels of waste edible oil differentiated by the source and so the respective quality. Also, only with government permission can recycling companies collect waste edible oil as the recycling standard set by government is quite high. After the permission, the city administration will irregularly go to the company to investigate whether the standard is maintained well. After the waste edible oil is recovered, it needs to be purified through residue filtration and oil-water separation (at present, eight collection and transportation enterprises in Nanjing all purify the oil according to this procedure). The purified waste edible oil can be used as an additive for the production of biodiesel or as a raw material for soap and other products. Mr. Sun also emphasized that the linolenic acid produced from our designed degradation pathway may not be used in human food and animal feed according to recent management announcements, but it still can be used as raw materials for cosmetics and some industrial products.
Public Security Bureau
---Ms. Yun Teng, Food, Drug and Environmental Crime Investigation Division, Public Security Bureau of Changzhou City
Ms. Teng helped us figure out how responsibilities are distributed among different supervision institutions. The public security branch mainly prevents the “gutter oil crime”, which is categorized as the criminal case. They have their own lab to quickly and accurately judge whether the situation forms a crime or not. As long there’s sufficient evidence to put on record, the criminal will be passed to the procuratorate and face serious punishment.
In the interview with Mr. Sun (Nanjing City Administration Bureau) that waste edible oil is divided into three grades: the oil taken from the sewer (poor quality), the oil filtered from the oil separator or swill bucket of the restaurant (average quality), and the oil filtered from KFC, McDonald's and hot pot restaurant (relatively high quality).Consequently, we investigated nearby restaurants and asked them how to identify gutter oil. More importantly, we focused on how they deal with waste oil and their views on gutter oil.
Discarded oil from eateries, including KFC, is classified as the highest level of gutter oil. The purpose of interviewing staff at KFC is to understand how they deal with the used oil and their opinions on gutter oil and our product to process gutter oil. KFC guarantees the use of oil by purchasing oil of a designated brand. They also have their own set of methods for identifying gutter oil: pure vegetable oil has no color. When they see many turbid objects in the oil or smell the smell of edible oil or minerals, it is likely to be gutter oil. KFC uses the oil filter paper and the quality testing machine to decide whether to replace frying oil. The oil used by KFC is of high quality, so its safety can be ensured. Discarded oil from KFC is classified as the highest level of gutter oil, so the recycling process is hardly impeded.
Weimin Restaurant (Shanxi Rd.)
Weimin is a breakfast eatery. Chinese people are used to have a power breakfast. As Chinese breakfast includes utilizing large amount of oil, the food safety of breakfast is of great importance. The staff told us that other than the illicit nature of using gutter oil again in cooking, the danger to customers’ health and potential complaint are what restaurants care more. They identified gutter oil through their experience. In addition, the recycling of used oil in Weimin is not as immediate as that in KFC, so there’s contamination to the environment within and around the restaurant. This might be due to the lower quality of used cooking oil from restaurant like Weimin, so recycling companies don’t treat them as the priority to collect oil from.
1.3 The public
After understanding the current situation of waste oil recycling, we also collected the public's views on this industry. Through online platforms and social media, we distributed a questionnaire to reflect the public’s awareness and understanding of gutter oil and its reuse methods. 446 individuals of different ages and education background participated, and below is the analysis of the result.The participants have various identities and backgrounds, which ensures the credibility and accuracy of the result.
Fig.4 Opinions about gutter oil supervision and reuse
According to the result, more than 80% of the population has limited knowledge of gutter oil, and there’s still 2% people having no idea of the concept “gutter oil”. Regarding the harmful substance in gutter oil, more people identify the existence of bacterial toxins than heavy metal. In general, most people are aware that gutter oil contains toxins and are not safe enough to be edible.
Fig.5 Attitudes towards biotransformation technology
All in all, the public survey offered our team a more comprehensive background regarding the public’s understanding of gutter oil and opinions of the biotransformation solution.
1.4 Feed back on our project
Recycling waste edible oil in the city is one of the key tasks of the regulatory authorities. Enterprises licensed to collect and transport waste edible oil will regularly collect waste oil from restaurants in the city. For restaurants, as long as companies collect waste oil (regardless of quality), they are more willing to cooperate with the legal recyclers.
We found that most people have been aware of the harm of gutter oil, although not enough. Our society needs to know that gutter oil can be reused in various fields. Only in this way can the gutter oil recycling industry flourish, and the means of biotransformation will also receive more attention. On the other hand, we also learned about the demand of all sectors of society for new methods of reusing waste oil. Although the current method can use waste oil to produce new substances, they are not entirely satisfactory.
2. Ideate Our Solution – the feasibility of our product
Though our project is valuable, its feasibility in actual industry needs to be evaluated, and fortunately, we received professional advice from team instructors, experts and other iGEM teams.
2.1 Team instrutor
---Dr. Yang Gu and Dr. Tianqiong Shi.
Firstly, we consulted ourteam instructors about the details of yeast industrial fermentation, including fermentation parameters and linolenic acid purification. The key part is the bioreactor with the function of containing gutter oil and yeast fermentation; The equipment directly connected to the bioreactor including the air compressor for conveying sterile air, the heater for maintaining 30 ℃ , and the motor for rotating propeller. The raw waste oil treated by the gutter oil recovery manufacturer is transported to the bioreactor for closed fermentation along the pipeline. After fermentation, all the liquid is transported to the large unloading centrifuge, and then the remaining solids from the centrifugation are transported to the plow mixer. 0.5N NaOH, 98% sulfuric acid and hexane are successively added to centrifuge the mixed liquid again, The centrifuged liquid is the linolenic acid stock solution we need, which can be further purified.
2.2 Fermentation expert
---Prof. Tianzhong Liu, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences
Professor Liu’s paper elaborates how his team utilizes wild wine yeast to produce palm oleic acid. There’re many similarities between their converting process and ours, so we emailed him to ask whether he would like to offer some advice in terms of the practicality of our project. To our project, he said the fermentation process is the same as the traditional oil-producing microbe, and ensuring the sufficient supply of oxygen is essential for the process. This makes us further think about the ventilation design of fermentation tank.
2.3 iGEM team in the same field
---HUST-China , 2021 iGEM team
After the preliminary design and construction of the 3D model of our team's hardware device, the team member in charge of the implementation part got in touch with HUST-China that also needed to design the fermentation tank, and held a meeting about the implementation part together. In the meeting, we shared the preliminary design of our device and introduced our 3D model. HUST-China then offered many useful and professional suggestions and provided us with some new solutions for some defects. They also gave us a lot of information about fermentation engineering, which played a great role in the subsequent improvements of our team’s device.
Fig.6 Online meeting with HUST-China
2.4 Feed back on our project--Fermentation expert
---Dr. Dongsheng Guo, Nanjing Normal University
We also got a chance to interview a specialist in fermentation engineering. This interview aimed to improve the model as Mr. Guo, a professor in the school of food science and pharmaceutical engineering of Nanjing Normal University, provided our member with several useful suggestions. Mr. Guo first answered in detail the questions raised by our team members about the detection system of various indicators in the fermentation tank. He then gave a perfect process for the follow-up processing of our products. After fully affirming the components of our whole model system, he also carefully put forward the design that needed to be carried out if it was to be applied to industrial production. Mr. Guo said that in the industrial mode, each equipment in our fermentation system may need a room to place, and the structure shown in our current 3D model is too crowded. The size of the fermentation tank depends on the fermentation capacity, so we must investigate the actual amount of waste oil treated by the factory. At the same time, we also need a room to make seed yeast liquid. After pre culture, yeast can grow rapidly in the fermentation process. He thinks we should go to the oil recycling factory to understand the equipment settings on the spot.
Fig.7 Online meeting with Dr. Dongsheng Guo
3. Implementation and Evaluation
Restricted by the unexpected COVID regional outbreak in Nanjing, some previously planned field trips were inevitably cancelled. We changed the original offline interview meeting to an online session and interviewed a professional of Dezhou Rongguang Biotechnology Co., Ltd. at online meeting room. Waiting until the aftermath of the pandemic ended, our members got a chance to visit a company that collects discarded oil from restaurants and school canteens all over Nanjing – Nanjing Yantai oil products company. The aim of the visit is to understand the current method of recycling and processing the gutter oil and get some opinions regarding our synthetic biology method.
3.1 Dezhou Rongguang Biotechnology Co., Ltd
In the beginning of August , we contacted Mr. Rongguang Li , a professional of Dezhou Rongguang Biotechnology Co., Ltd. , and conducted the interview at the Tencent conference.
Fig.8 Chat with Mr. Li Rongguang at Tencent conference
3.1.1 Source of gutter oil
The company uses a wide range of sources of gutter oil. The primary source is food waste treatment plants. Legal food waste treatment plants or collection companies in each city contact the waste disposal site and separate waste oil from the garbage. In addition, gutter oil comes from food factories and other units: all waste animal and vegetable oils in the catering industry. More specifically, manufacturers and units that produce ham sausage from animal meat also have gutter oil; French fries in fast-food restaurants such as McDonald's contain gutter oil. The available oil production price is around 7,000RMB per ton.
3.1.2 Waste oil pretreatment
The manufacturer responsible for the conversion of waste oil before purchasing does not need to do pretreatment. The kitchen waste manufacturer carries out the treatment. The manufacturer separates the waste oil from the food and kitchen residues in solid and liquid. The waste oil is more pure and clean in production and processing, and it is convenient for further processing.
3.1.3 Processing method
The company's product line produced using waste oil has the following parts: raw material (waste oil) storage tanks, pre-esterification tanks, continuous lipidation tanks, lipid exchange tanks, precipitation tanks, distillation towers, and finished product tanks (biodiesel).
3.1.4 Feed back on our project
The lipidation process is the most important. Glycerates go from the state of fatty acids to the form of methyl esters. The higher the methyl ester content, the higher the quality of the product. When using yeast for oil conversion, the most important thing is to use protease for an experiment. It needs to be stirred thoroughly to prevent agglomeration and poisoning. Ensure acid-base balance and avoid protease from losing activity. In the production process, controlling costs is very important. Every link needs to control costs. Control the impurities in the purchase of raw materials; control the amount of catalyst and temperature during the fatification process; control the yield during distillation; control the personnel and labor expenditure; control the automation cost.
Fig.9 Mr. Li illustrates the industrial process of oil conversion
3.2Nanjing Yantai oil products Co., Ltd
In the face-to-face interview with sufficient social distance, Miss. Zhang, the director of technicians, and Mr. Shao, the manager of the factory, told us the current situation of gutter oil recycling.
3.2.1 Smooth recycling process
Miss. Zhang told us that the collecting process is always carried out with little barrier since there’s policy requiring all eateries to dispose their waste oil by selling them to recycling companies like Yantai. Though the return of converting gutter oil into edible oil is a few hundred higher than selling it to recycling companies, the illicit nature discourages many retailers from turning to the former approach.
3.2.2 Low requirement for recycling
The threshold of the recyclable gutter oil is low: discarded kitchen oil with relatively little amount of residue is acceptable, which covers most of oil disposed and reduces the flow of waste oil to illegal production of cooking oil.
Fig.10 Cars used to collect gutter oil
3.2.3 General processing procedure
Led by Mr. Shao into the operation section, we witnessed how the gutter oil is processed to exclude Impurities. The first step is to heat the raw oil with extremely high temperature to separate oil and water by their high temperature, then the oil passes the filter facilities to separate coarse and large particle. Further filtered the more refined impurities through pressing. The final processed oil will be bought by companies that manufacture different products from the processed oil.
Fig.11 High temperature heating systems in the plant
3.2.4 Feed back on our project
Miss. Zhang showed great surprise and expectations on our project. She said, “China hasn’t got a cost effective way to ‘turn waste into treasure’ for gutter oil, so most of the high-quality biodiesel is produced by foreign companies from the processed oil exported from China to other countries. The profit is still limited. The domestic industry is in the ‘bottleneck’. I hope your guys can contribute to the breakthrough.” The large coverage of collecting gutter oil ensures the supply of oil for further manufacturing, The demand for new methods of using gutter oil shows that our products have broad prospects for further application.