NEW STRAIN PRODUCERS OF BIOBUTANOL. III. METHODS OF INCREASED BUTANOL ACCUMULATION FROM BIOMASS OF SWITCHGRASS Panicum virgatum L.

Nowadays the world market of butanol exceeds 9.6 billion liters and is assessed at more than 6.0 billion US dollars [1]. There is a stable trend towards yearly increase (by 3.2%) of demand for butanol. Butanol is used as a solvent for industrial production, in production of melamine-formaldehyde resins and plasticizers, butyl acetate, butyl acrylate and in organic synthesis. Besides, it has begun to be actively used as fuel. Only 0.1 % of total butanol production goes to microbiological synthesis, and compared to other biofuel types its share is only 2%. Experts forecast that in the next 5–10 years this value will reach 30% [2]. Unfortunately, today the microbiological method of butanol production is not efficient due to formation of by-products such as ethanol and acetone during the cultivation, relatively high cost of feedstock, low strain productivity, and the problem of waste disposal — acetone-butyl spent grains. To optimize the process of metabolite production it is necessary to perform the following: carry out the primary selection of producer strains, make changes in genetic structure of strain-producer to increase the product accumulation, define the optimal technological parameters (pH, temperature, nutrient requirement) and conditions for nutrition and biomass accumulation and chose the way for cell-producer immobilization [3–10]. In case of using the reducing and considerably cheap plant biomass, it is necessary to create profitable technology of acetone-butyl fermentation and production of solventogenic strains. The aim of this study was the increase of butanol accumulation from the biomass of switchgrass