Thermophilic bioprocessing of lignocellulosic waste-materials for generation of energy

    Cellulosic waste-materials including agricultural wastes are among the Earth's most abundant renewable resources and are a major concern in energy generation and environmental restoration.  We have been trying to understand fundamental microbiological and molecular approaches in bioconversion of polymeric cellulosic waste materials using thermophiles from local compost facility and a deep underground mine, Homestake Gold Mine, Lead, South Dakota.  On July 10, 2007, the National Science Foundation designated this deepest mine in North America as the site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL).  During active mining operations over 125 years, surface microbes and lignocellulosic substrates were introduced into the extreme environments of the subsurface.  Interactions between introduced and existing microorganisms through horizontal genetic transfer might have caused genome-altering events.  Thus, it is believed that DUSEL represents a potential source of high-value microbial enzymes.  Our main objectives are to: 1) use novel thermophiles in conversion of cellulosic waste-materials, and 2) establish genomic bases of thermophilic microbial digestion of cellulosic waste-materials. 

Heavy metals and uranium inhibition and detoxification mechanisms

    The fate and transport of uranium and heavy metals in groundwater depend significantly on the activity of subsurface dissimilatory metal reducing bacteria such as sulfate reducing bacteria (SRB), which can precipitate highly soluble metals using enzymatic as well as non-enzymatic processes. Therefore, effective manipulation of indigenous bacterial communities to stimulate in situ activity in the presence of toxic heavy metals requires knowledge of the toxic effects of contaminants on subsurface bacteria.

The effect of biogeochemical interactions on the stability of contaminant (metal) precipitates

Uranium is the most common radionuclide in soils, sediments and groundwater at many sites including US Department of Energy sites and is therefore of particular environmental concern. Subsurface bacteria such as sulfate reducing bacteria (SRB) can reduce highly soluble U(VI) to less soluble U(IV) under anoxic, circumneutral pH conditions.
 

Tooth decay mechanisms

           We recently initiated research work on tooth decay. It has been suggested that bacteria present in tooth oxidize sugars to acid and the produce acid degrades the tooth. However, these tooth decay mechanisms have not been shown in vitro conditions. Therefore, we really want to understand mechanisms of the tooth decay using pure as well as mixed cultures. I have been collaborating with Professors Amit and Susmita (Material Science Department, Washington State University) who synthesized fake teeth (mainly composed of calcium phosphate ceramic). We are treating those fake teeth with sulfate reducing bacteria (which are known to play role in tooth decay). In the absence of sulfate reducing bacteria, we did not see any decay; however, in the presence of sulfate reducing bacteria after 44 days we saw some tooth decay(see figure below). Using these preliminary results, we plan to write a proposal to National Institute of Dental and Craniofacial Research very soon.

The structure and function of microbial communities of contaminated sediments

   High levels of heavy metals are present in the sediments of Lake Coeur d'Alene in Idaho and their   presence is mainly the result of historical mining in the mountains upstream.This project is focused on the development of a dynamic numeric biogeochemical model of heavy metal cycling in LCA sediment systems and the role of the whole microbial community in biogeochemical cycling of metals.