Rajesh Sani
South Dakota School of Mines and Technology, USA
Title: Extremophiles in biofuel synthesis from solid wastes
Biography
Biography: Rajesh Sani
Abstract
More than 34% of a typical solid waste are food, wood and yard waste whereas paper and paperboard contribute to another
25% to the ever increasing issue of waste management and its disposal. To date physiochemical pretreatment of solid
wastes has been shown a necessary step for previously listed consolidated biological processes which increases the overall cost
of the process e.g., plant biomass is inexpensive ($2-4/GJ at a cost of $39-60/dry ton biomass) but its pretreatment cost ($15-25/
GJ) dramatically reduce the overall cost-effi ciency of the process. An alternative to the bioprocess involving pretreatment is the
development of an effi cient and cost-eff ective single step process for untreated solid waste management using extremophiles.
For example, thermophiles and their enzymes can play important roles in many kinds of bioprocessing including in conversion
of non-food biomass into biofuels. Th e Homestake gold mine (8000 ft . deep, Lead, SD) off ers a unique opportunity for direct
exploration of the deep biosphere environment. Using soil/biofi lm samples of deep biosphere of the Homestake Gold Mine,
compost facility (Rapid City, SD) and Hot Springs State Park (Th ermopolis WY), we have isolated several thermophilic
cellulose and xylan-degrading and fermenting pure cultures belonging to the genera Brevibacillus, Paenibacillus, Clostridium,
Bacillus and Geobacillus. Unique characteristics of lignocellulose-deconstructing enzymes produced by mine and compostthermophiles
include optimum temperatures of >70ºC, pH ranges from 4-8 and high thermostability (e.g., at 60ºC, 50%
of cellulases and xylanases activities were retained in 35 and 23 days of incubation, respectively). Our thermophiles also
produced biohydrogen or bioethanol in a single step bioprocessing of various inexpensive regional untreated biomass (e.g.,
prairie cord grass and corn stover). Th is talk will describe the limitations in exiting solid waste conversion technologies and
possible ways to overcome those limitations using thermophiles and their enzymes. Th e infl uence of high temperatures on
various existing lignocellulose conversion processes and those that are under development, including separate hydrolysis
and fermentation, simultaneous saccharifi cation and fermentation and extremophilic consolidated bioprocess will discussed.
Integrated decentralized thermophilic biofuel production employing cellulolytic and fermentative thermophiles in a single
step consolidated process will also be discussed.