Comments of WSPC Research Council
Dr. Chen,
Yesterday afternoon the research council discussed your proposal, and recommended that it be invited to the final research review in February, but with some revision. The major point of contention was the economic analysis of the benefits of the project. Apparently cull potatoes are sometimes far more valuable that you assumed. It was suggested that you dispense with the economic analysis altogether, or attempt to incorporate a cull potato price of $60/ton rather than $10. There was also some confusion about how large is the world demand for DHA and EPA, and how many potatoes would be required to generate those amounts. Some had gotten the impression that one 100 acre field of potatoes would be enough. You might be sure to make this clearer in the revised proposal. Also, there was a comment that sugar must be cheaper than potatoes. The person was probably thinking of sucrose from beets. You might touch on this issue as well.
Finally, it was suggested that perhaps waste water from processing plants would be a more economical source of starch. Processors have tried over the years to figure out good ways to make use of this starch, but have so far been unsuccessful. It was suggested that the best use of it might some kind of flow-through process.
The final research review is in Pullman on February 10-11 at the Holiday Inn Express. Revised proposals are due to me by January 15. I will be in contact with you in late January about your presentation date and time.
Please contact me with any concerns or questions.
Regards,
Andy Jensen
Andrew Jensen, Ph.D.
Director of Research
WashingtonState Potato Commission
108 Interlake Road
MosesLake, WA 98837
Phone: 509-765-3680
Fax: 509-765-4853
E-mail:
Replies to the research council’s comments
- It was suggested that you dispense with the economic analysis altogether, or attempt to incorporate a cull potato price of $60/ton rather than $10.
In the original proposal, we made several assumptions in order to estimate the profitability of algae production process. The assumptions are: (1) using pure glucose to produce algae results in a negative $1 profit/loss margin for each kg algae produced, (2) the pure glucose cost in the algae production process is $1.6/kg algae biomass produced, and (3) wet cull potatoes contain 15% starch and the conversion yield from potato starch to algal biomass is 40%.
Assumption (1) indicates that compared to the pure glucose-to-algae process, the potato-to-algae process should save at least $1 in order to make the process profitable. We believe that this $1 cost-saving can derive from using cheap cull potatoes. Furthermore, sincethe pure glucose costs $1.60 (Assumption 2), the potato cost contribution should be no more than $0.60 (“break-even” cost). From assumption (3), we derived that each ton of wet potatoes would produce 60 kg algal biomass. (1 ton wet potatoes15% starch content40% yield=60 kg algal biomass).
Based on the above estimation, when cull potatoes are sold at $10/ton, the feedstock cost in potato-to-algae process will be $0.167/kg algae biomass, which when compared with the “break-even” cost ($0.6)results in a $0.433 profit. When cull potatoes costs $36/ton, the potato cost will be $0.6/kg algae biomass, which is the “break-even” cost. Thus, when the cull potatoes aresold at $60/ton, the potato-to-algae process seems un-profitable, however, we believe that several efforts proposed in this project could make the potatoes-to-algae process economical viable even at such a high price. These efforts include:
(i). Increasing the conversion yield of algae biomass. Typically, the yield of algal biomass from potato starch is around 40% - 60%. In the original proposal, we conservatively chose 40%, so 1 ton of cull potatoes could only obtain 60 kg algae biomass. In our new research plan, we will focus on increasing the algae biomass yield through process optimization and high cell density algal fermentation. If we increase the yield to 60%, 1 ton of cull potatoes could produce 90 kg algae biomass. This means the break-even sell price for cull potatoes will increase from $36/ton to $54/ton. If the yield hits 67%, which is moderately high but not unrealistic, the break-even price would be $60/ton! So our first research efforts will be increasing the algae production yield to at least 67%.
(ii). Reducing the algal fermentation cost by using wastewater from potato processing plants. In algae fermentation processes, carbon source (either pure glucose or potato starch) is a major cost. However, other nutrients such as nitrogen, phosphorus, various salts, trace elements and vitamins are also required and thus contribute to the algal fermentation cost also. Using the wastewater from potato processing plants could provide partially, if not totally, the required amounts of starch and other nutrients needed for algal growth. This could significantly reduce the total processing cost of potatoes-to-algal fermentation by not requiring the need for nutrient or even starch supplementation from far more expensive sources. Indeed, the solid and liquid waste produced in the potato processing plant does contain various micronutrients, which are ideal for algal growth. This has been confirmed by our communications with the staff at a potato processing plant (Lamb-Weston, Inc.) in Connell, WA in year 2003(data not shown as confidential request). The details of this research plan have also been addressed in the revised proposal and “Replies to Comment 4”.
(iii) Finally, we believe that $60/ton is the upper limit of cull potatoes price although our inquiries into confirming this have not produced results as of yet. As a result, though, given this value as an upper limit, the price could reach this level sometimes, but may not be maintained all the time and thus may not have as drastic an effect on the economics as is being feared.
In summary, although cull potatoes could be sold at $60/ton sometimes, we still have the capabilities to make the proposed potato-to-algae process economical viable. The above issue hasalso been addressed in ANTICIPATED BENEFITS section of the revised proposal.
- There was also some confusion about how large is the world demand for DHA and EPA, and how many potatoes would be required to generate those amounts. Some growers had the impression that one 100-acre field of potatoes would be enough. You might be sure to make this clearer in the revised proposal.
According to research reported by Lebeau and Robert (Diatom cultivation and biotechnologically relevant products, part II: current and putative products, Applied Microbiology and Biotechnology, 2003, 60: 624-632), world-wide EPA demand is around 300 tons per year. We used this number to estimate the required cull potatoes if all the EPA is produced by the potato-to-algae process.
Algae biomass generally contains 2-3% EPA, if taking 2% EPA content, the required algae biomass to produce 300 ton EPA would be 15,000 ton (algae). Assuming conversion yield from potato starch (dry weight) to algal biomass is 67%, and fresh cull potatoes contain 15% dry starch, the required fresh cull potatoes for this 15,000 ton algae would be around 150,000 ton or 330 million pounds(fresh cull potatoes). We estimate potatoes are harvested at an average of 60,000 lb/acre with 10% being culls, thus each acre will produce 6,000pounds of cull potatoes or when enlarging the ratio, 330 million poundsof cull potatoes would require around 55,000 acres. In summary then, each year, 55,000 harvested potato acres will be needed to produce 330 million pounds of cull potatoes, which can be finally converted to 300 tonnes of EPA.
The annual DHA demandappears to be of the samemagnitude as that of EPA, because DHA plays the similar functions as EPA and most omega-3 products are added with EPA/DHA simultaneously. By assuming the same demand of DHA as EPA, we have estimated, then, that each year, at least 110,000 acresof potatoes are needed, provided all EPA and DHA are produced by a potatoes-to-algae process.
Although the above estimation is very rough, it clearly shows that the potential demand for cull potatoes is much larger than the 100-acres quoted by those that had earlier worries. Also be reminded that with more and more clinical evidences about EPA/DHA’s beneficial effects, more consumers will realize the importance of these two fatty acids. The above issue has been addressed in ANTICIPATED BENEFITS section of the revised proposal.
- There was a comment that sugar must be cheaper than potatoes.
Here, we believe the sugar referred to was sucrose from beets.Sucrose is a disaccharide containing oneglucose and one fructose unit. For the algal fermentation, however, sucrose is considered not a good substrate for several reasons:
(i). Most algal species cannot utilize sucrose at all or utilize it at a very low efficiency in terms of algal growth and EPA/DHA production. The reason is that sucrose is too “big” to pass through the cell membrane by diffusion.
(ii). Sucrose can be hydrolyzed into glucose and fructose. However, the hydrolysis requires either acid, which is not environmental friendly; or enzyme (e.g., baker's yeast invertase), which is expensive compared with industrial amylase for starch hydrolysis.
(iii). Even if a cost-effective sucrose hydrolysis method is developed, it will produce half glucose and half fructose. Glucose is a good carbon source for algae. Fructose, however, can not be utilized as efficiently as glucose by most algal species and thus would be in sorts a wasted product.
Conversely, starch is an ideal carbon source for algal growth. The DHA producing alga proposed in the project (Thraustochytrium aureum, ATCC 34304) can directly utilize starch. The reason might be that the alga produces -amylase, which can convert starch into glucose (Bajpai et al., Optimization of production of docosahexaenoic acid (DHA) by Thraustochytrium aureum ATCC 34304. Journal of the American Oil Chemists Society, 68: 509-514). Although EPA producing alga can not utilize starch directly, and enzymatic hydrolysis is needed to convert starch into glucose, the enzymes used in the starch hydrolysis (-amylase) are very cheap, especially in its industrial grade. In addition, the SSF fermentation method proposed can greatly enhance the hydrolysis efficiency by reducing end-products inhibition.
In summary, we believe that potato starch is a better carbon source for algal growth than beet sugar, although the latter mightbe cheaper than cull potatoes.
- Finally, it was suggested that perhaps waste water from processing plants would be a more economical source of starch. Processors have tried over the years to figure out good ways to make use of this starch, but have so far been unsuccessful. It was suggested that the best use of it might some kind of flow-through process.
As kindly suggested by the council, we modified our research plan by using the wastewater from potato processing plants. This will reduce, if not totally avoid, the addition of nutrients to be externally added. The nutrients of the processing plant waste will be analyzed in terms of its starch content, nitrogen, phosphorus, sodium, calcium, potassium, and other trace element by Water Quality Lab at WSU. The final recipe of added nutrients will be the standard nutrient concentrations subtracted by those at the waste stream. (Please also refer PROCEDURES (1) & (2) of the revised proposal and “Replies to Comment 1, Part (ii)” for related address).
TITLE:Production of Omega-3 Polyunsaturated Fatty Acids from Cull Potato
YEAR INITIATED: 2005.
CURRENT YEAR: 2004.
TERMINATING YEAR: 2007
PERSONNEL:
Dr. Shulin Chen (Dept. of Biological Systems Engineering, WashingtonStateUniversity,
Phone: 509-335 3743, email: )
Dr. Zhiyou Wen (Dept. of Biological Systems Engineering, WashingtonStateUniversity,
Phone: 509-335 3859, email: )
Dr. Ron Kincaid (Dept. of Animal Science,WSU, Phone: 509-335 2457, email: )
JUSTIFICATION:
This project is to develop a cost-effective algal cultivation process converting cull potato starch to -3 polyunsaturated fatty acids (-3 PUFA), i.e. eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), that have beneficial effects in treating and preventing human heart and immune diseases. The -3 PUFA enriched algal biomass could be used as feed additives for dairy to enhance the nutritional value of the milk. The project addresses the potential interest of Washington State Potato Commission. i.e., nutritional enhancement of potatoes, new food uses for potatoes, and alternative uses of potatoes in chemical manufacturing or pharmaceuticals.
Ever since potatoes have been sorted for quality and size, growers have been faced with a part of their crop found to be very low in value. For every acre of potatoes harvested, 10 to 15 percent of the crop that is graded culls. This includes undersized tubers, bruised, damaged and deformed tubers, and tubers unfit for market.Cull potato costs the growers $70 to $120 per ton to grow, and even iffarmers could receive as high as $60/ton to sell those culls,the growers must pay the remaining negative cost of growing these culls out of income from the marketable grades. Clearly, the inclusion of value-added components will be necessary in order to attain profit margins for farmers.
DHA and EPA processed from the algal fermentation of cull potatoes are capable of providing this new level of profitability for the farmers. DHA is the component of the photoreceptor cells of infant retinas and is also involved in the development of infant brain tissue. The inclusion of supplementary DHA in infant formulas is strongly recommended by the World Health Organization. EPA possesses therapeutic activities againstcardiovascular diseases, cancers, schizophrenia, bipolar disorder, and most recently noted, alzheimers. Both of these two fatty acids unfortunately cannot be synthesized by the human body.Fish oil is currently the conventional source of DHA/EPA. However, there are some limitations of fish oil as a source such as peculiar taste, odor, stability problems, and the difficult and expensive purification of these acids from low-grade fish oil. The fish stocks are also subject to seasonal and climatic variations. It is reported that fish, like humans, are not capable of synthesizing PUFA de novo. Much of their PUFA is derived from the primary producer: the microalgae.
The proposed project offers an attractive alternative for PUFA production from cull potatoes. In addition, the -3 PUFA enriched algal biomass could be used as feed additives for some animals such as cows to transfer the -3 PUFAs from algal biomass to milks. The proposed project is unique in that: (1). it reduces the cost of feedstock for algal cultivation by using cull potatoes, and (2) it avoids the cost of purifying -3 PUFA from algal biomass by using cow as “extractor”. The project is also beneficial to Idaho and Organ state as potato is a major agricultural products and incomes for the local farmers.
OBJECTIVES:
Objectives in this project include:(1) optimizing the algal culture Thraustochytrium aureum for DHA production through direct use of cull potato starch; (2) optimizing the algal culture Nitzschia laevis for EPA production from potato starch through a simultaneous scarification and fermentation (SSF) process; (3) developing a high cell density for algal cultivation, (4) pilot study of the algae cultivation process, and (5) assessing the possibility of using algal biomass as additives in cattle feed.The Objectives (1) and (2) will be addressed during the first funding year (i.e. 04/01/2005-31/03/2006).
PROCEDURES:
(1). Optimizing the algal culture for DHA production through direct use of potato starch
Thraustochytrium aureum (ATCC 34304) will be used for DHA production since the alga can directly utilize starch as a carbon source for DHA production (Bajpai et al., 1991), thereby removing the need for and cost of converting starch into glucose. A medium for T. aureum growth will be prepared by boiling fresh cull potatoes in water to obtain a liquefied starch that will later be mixed with other nutrient solutions including some mineral salts, yeast extract and traces of vitamin B12 and biotin. Usually, the carbon source, at 3~4% of the medium mass, is the major cost contributor as all of the other components are used in a very low level that is well less than 0.1% of the total. Thus, using under-valued cull potato to replace glucose as a carbon source can significantly reduced the medium cost and ultimately the price of the whole process. In addition, optimization might eliminate the need for some of the added nutrient components as potato might be determined to be a capable provider.
To reduce the medium cost, the wastewater from potato processing plant will be used. The pure water is used as control. The nutrients of the processing plant waste will be analyzed in terms of its starch content, nitrogen, phosphorus, sodium, calcium, potassium, and other trace element by Water Quality Lab at WSU. The final amount of added nutrients will be the standard nutrient concentrations (control) subtracted by those at the waste stream.
The cultural conditions for the algal culture will be optimized by first adding the cooked cull potato material to solution at four levels (10, 20, 30, 40 g/l), and measuring the resulting corresponding DHA yield. Once the optimal potato concentration is determined, a complete statistically-based experimental design will be used to optimize the other medium components as well as temperature and pH. The design includes three major components: (1) selection of significant factors influencing DHA production by a Plackett-Burman design; (2) optimization of the significant factors by a central composite design; and (3) verification of optimal conditions. All of the above experiments will be conducted by flask cultivation. The algae will be harvested for analyzing their DHA content. The algal biomass will be freeze-dried and its lipids/fatty acids will be extracted by standard AOCS methods (The American Oil Chemists’ Society). The fatty acids will then be analyzed by a gas-chromatography (GC).