Southeastern Sun Grant Center Quarterly Progress Report
Project Title: Biological energy production from biomass by wood-feeding termites Recipient Organization: Mississippi State University Principal Investigator: Dr. Jianzhong Sun, Dr. Yueqing Cao, Dr. Jose Rodriguez Project Location: [Poplarville, MS; Starkville, MS.] Reporting Period: [July 1, 2008 to September 30, 2008] Date of Report: [March 6, 2009] Written by: [Jianzhong Sun]
1. Planned Activities: [Understand how bioconversion efficacy of H2 from cellulosic
substrates by wood-feeding termites. Enhance H2 production via modifying termite luminal symbiotic bacteria which uptake H2 by methanogens, acetogens, as well as other aerobic bacteria]
2. Actual Accomplishments: [The discussion should include all significant work
completed in the past quarter to support the project and accomplish goals.]
Hydrogen emission by wood-feeding termites, Coptotermes formosanus,
Reticulitermes flavipes and Reticulitermes virginicus, when feeding on cellulosic substrate, was investigated during a 72 h incubation period. The emission rates among three species tested were significantly different and R. virginicus demonstrated the greatest H2 emission at 4.78 ± 0.15 µmol /h/g body weight. In a sealed test apparatus, H2 emission for each termite species showed a quick increase at the initial incubation hours (3-6h) followed by slower growth, possibly due to the feedback inhibition by gas accumulation. Further investigations revealed that a continuous H2 emission could be maintained when H2 partial pressure was lowered. The bioconversion of cellulose to molecular H2 via the termite gut system could reach as high as 3858±294 µmol/g cellulose, suggesting that a novel H2 ecosystem and the relevant hindgut symbionts would thus offer an opportunity to assist current biological H2 generation.
A study has been conducted to evaluate the H2 production by a wood-feeding
termite, Coptotermes formosanus, when four antibiotics, ampicillin, metronidazole, gentamicin, and tetracycline, were applied to its cellulose diets. The results showed that the H2 emission rate of C. formosanus varied significantly among the four antibiotics investigated. The highest H2 emission rate by this termite was recorded as high as 1900 nmol/h/g body weight at ampicillin antibiotic treatment, which was about 7 times of the control groups. Termite diets treated with tetracycline and metronidazole at 50-100 µg/ml would also enhance the termite H2 emission significantly, which was 3-6 times of the control groups. However, the diets treated with gentamicin at 1-100 µg/ml did not show any increase in H2 emission rate by the termites tested.
The further investigations were also conducted for the effects of antibiotics on gut
symbionts, such as protozoa communities, spirochete bacteria, as well as the amount of acetate synthesized in termite hindguts after diets were treated with varied antibiotics at different concentrations. It seems likely that these antibiotics have no any observable adverse effects on the activities of symbiotic protozoa that are mainly responsible for lignocellulose decomposition and H2 production. However, the activities of some
symbiotic bacteria, such as spirochete, methanogens, and acetogens that were free swimming at hindgut, were significantly suppressed, which led to a significant boost of H2 production probably due to the less consumptions of molecular H2 by acetogenic bacteria for synthesizing acetate product in termite hindguts.
The investigations with confocal laser scanning microscopy (CLSM) also confirmed
that the majority bacteria (75% of the total gut bacteria) symbiotic within the protozoa cells, Pseudotrichonympha grassii and Holomastigotoids hartmani, in termite hindgut were not negatively affected by the diets treated with antibiotics in terms of their quantity and functions, where these two flagellate species are mainly responsible for cellulose decomposition and H2 production in termite gut system.
There were no observable changes in termite foraging behavior, cellulose
consumption rate, as well as the colony survival rate for a period of 10 days’ feeding on the treated diets. This study further suggests that H2 production from termite gut by C. formosanus could be improved significantly with a selected antibiotic at a balanced concentration on cellulose diet, where the activities of H2 uptake bacteria (free swimming in termite gut lumen) were suppressed for their H2 consumption.
3. Explanation of Variance: [This section should discuss any differences between the
planned activities (section 1) and the actual accomplishments (section 2). These differences should be included even if the setback was out of the control of the recipient, such as a change in the availability of equipment and/or facilities. Issues, concerns, successes or requested changes and the resulting impact to the project objectives, budget and/or schedule should be discussed.]
4. Plans for Next Quarter: [Planned activities to be conducted during the next quarter
In order to acquire a continuous hydrogen production from termites, an optimal
environment and life secured system applied for a colony of termites is required to develop. Thus, some parameters associated with termite life system should be investigated with respect to oxygen consumption rate by termites, the possible negative effect caused from those noxious gases emitted by termite themselves (such as CO2, CO), as well as a ventilated gas collection system adapted to a termite life system.
Patents: [NA] Publications / Presentations: Oral presentation:
Sun, J.-Z. 2008. “The present state of art for lignocellulose-feeding insects: an emerging and
promising area of entomological science”, The 55th Annual conference of the Mississippi Entomological Association. Oct. 24-26, 2008. Starkville, MS.
Sun, J.-Z. 2008. “Biological energy production from biomass by wood-feeding termites”, The 56th
Annual Meeting of the Entomological Society of America, Nov. 16-19, 2008, Reno, NV (Invited). Referred paper:
Cao, Y. -Q, Sun, J.-Z., Rodriguez, J. M., and Lee, K. C. 2009. Hydrogen emission by three
subterranean termite species (Isoptera: Rhinotermitidae): their production and characteristics. Int. J. Hydrogen Energy. In reviewing.
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