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United States Department of Agriculture

Agricultural Research Service


Location: Tropical Crop and Commodity Protection Research

2011 Annual Report

1a. Objectives (from AD-416)
The goal of this agreement is to carryout a collaborative research effort among PBARC, The College of Agriculture, Forestry and Natural Resource Management (CAFNRM) at the University of Hawaii at Hilo (UHH), and the College of Tropical Agriculture and Human Resources (CTAHR) at the University of Hawaii at Manoa (UHM) that addresses important agriculture problems in Hawaii. The specific problem to address is determined through consultation and agreement among the agriculture college deans of CAFNRM and CTAHR and the director of PBARC. The main objective of this SCA is to evaluate the usefulness of regionally grown feedstock for aquaculture and livestock.

1b. Approach (from AD-416)
In 2002, congress provided a set amount of funds to PBARC with the mandate that the funds should be split three ways among CAFNRM, CTAHR, and PBARC. The intent is to develop a mutually beneficial collaborative research effort that is formulated by the deans and the director of PBARC. The deans of CAFNRM and CTAHR, and the director of PBARC met and agreed to develop a research effort to evaluate the usefulness of regionally grown feedstock and co-products for aquaculture and livestock. Each institute would focus on research areas in which they have strengths and which would move the institutions closer to achieving the stated objective. To carryout the research plan, each dean will put out a call for proposals to their respective colleges for grant proposals to address the objective over a five year period. The proposals will be reviewed and selected by the deans and the director of PBARC, and any advisors that they may choose. To ensure that the research is focused on the objective and to assess progress, the investigators of the selected grants, the deans, and the director will meet annually to evaluate the work. Following the annual meeting, changes in the research personnel or focus may take place if needed. PBARC will have a research effort towards this objective but it will not have a call for proposals since the funds originally allocated to PBARC became part of their base budget. To maintain a degree of flexibility, the deans may use a small part of the funds to support other projects that may not be directly related to the main objective. Formerly 5320-43000-015-07S (June, 2011).

3. Progress Report
Growth of the fungus Rhizopus microsporus var. oligosporus on crude glycerol (biodiesel derived byproduct) was found to be optimal at a starting pH of 5.0, temperature of 37 C and using nonsterile crude glycerol (75% (w/v)) with nutrient supplementation. Results of the laboratory-scale trials showed that production costs could be lowered by eliminating pH control and initial substrate sterilization, which greatly simplified the conversion of fungal protein from glycerol. Another study showed that significantly higher fungal biomass yields observed in banagrass juice supplemented samples compared to laboratory nutrient-supplemented samples, suggesting a synergetic effect of banagrass juice for fungal growth on crude glycerol. The improvement of fungal biomass yields for banagrass juice supplemented glycerol samples was 2.31-fold higher than that of the control sample. This supports the potential of utilizing a low-cost banagrass juice as a source of nutrients for enhanced fungal protein production. Other biofuel byproducts that were investigated were those derived from phytoplankton. Initial analyses of the phytoplankton byproduct showed that the protein levels were acceptable for the culture of omnivorous species (e.g., tilapia, prawns) but might require supplements for carnivorous species. Conversion of organic material by saprophages has gained in popularity over the last decade and larvae of the black soldier fly (BSL) Hermetia illucens have been shown to be capable of converting large amounts of organic waste into protein rich biomass. The grubs reportedly could serve as a substitute for fishmeal or fishfood. Efforts using feral tilapia as substrate resulted in food conversion ratios (FCR) of only 3.9 ± 0.7% in live grubs. The low recovery value was attributed to the large amount of indigestible matter (e.g., bones, scales) that remained. There is a potential that biofuel byproduct based feeds may not fully support the growth potential of fish. Myostatin prodomain (MSTNpro) was reported to suppress the bioactivity of myostatin, a potent negative regulator of skeletal muscle growth. It was hypothesized that suppressing myostatin activity in tilapia by an immersion bath treatment with recombinant flounder MSTNpro would improve the growth of tilapia. Results of the study showed that the immersion bath treatment with both 0.05 and 0.2 mg/L MSTNpro significantly increased the body weight and length of tilapia at 2 weeks after the last immersion bath treatment. However, no significant difference in body weight and length was observed at 41 weeks after the last immersion bath treatment. Weights of liver, heart, and fillet were not affected by the immersion bath treatment with MSTNpro. The current results suggested that myostatin suppression by MSTNpro immersion bath treatment during early juvenile period was able to enhance tilapia growth for a short period after the treatment, but this effect disappeared during an extended growth period (45th week). Project was monitored via meetings, visits, and telephone and email communications.

4. Accomplishments

Last Modified: 06/25/2017
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