Aerobic and anaerobic cellulase production by Cellulomonas uda
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ORIGINAL PAPER
Aerobic and anaerobic cellulase production by Cellulomonas uda Henrik Vestergaard Poulsen1 · Fillip Wolfgang Willink1 · Kjeld Ingvorsen1
Received: 25 February 2016 / Revised: 8 April 2016 / Accepted: 25 April 2016 © The Author(s) 2016. This article is published with open access at Springerlink.com
Abstract Cellulomonas uda (DSM 20108/ATCC 21399) is one of the few described cellulolytic facultative anaerobes. Based on these characteristics, we initiated a physiological study of C. uda with the aim to exploit it for cellulase production in simple bioreactors with no or sporadic aeration. Growth, cellulase activity and fermentation product formation were evaluated in different media under both aerobic and anaerobic conditions and in experiments where C. uda was exposed to alternating aerobic/anaerobic growth conditions. Here we show that C. uda behaves as a true facultative anaerobe when cultivated on soluble substrates such as glucose and cellobiose, but for reasons unknown cellulase activity is only induced under aerobic conditions on insoluble cellulosic substrates and not under anaerobic conditions. These findings enhance knowledge on the limited number of described facultative cellulolytic anaerobes, and in addition it greatly limits the utility of C. uda as an ‘easy to handle’ cellulase producer with low aeration demands. Keywords Cellulose degradation · Cellulase · Cellulomonas uda · Facultative anaerobe · Aerobic/ anaerobic
Communicated by Erko Stackebrandt. * Kjeld Ingvorsen [email protected] 1
Department of Bioscience, Section for Microbiology, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark
Introduction Cellulose, a linear polymer of glucose molecules joined by β-1,4-glycosidic-linkages, is the most abundant biopolymer on the planet and strongly resistant to biodegradation (OSullivan 1997). Over the past few decades, the conversion of cellulose-containing biomass to various fuel products has been actively researched as a sustainable solution to future energy demands (Himmel et al. 2010). However, the efficient use of cellulosic materials requires a costly enzymatic pretreatment, presenting a major obstacle to economical production of cellulose-based biofuels (Wilson 2009). The vast majority of described cellulase-producing microorganisms are either aerobes or anaerobes, and members of these two groups produce cellulase by very different strategies. The aerobes generally excrete their cellulolytic enzymes, whereas most of the anaerobes possess cell-bound organelle-like structures (cellulosomes), containing several catalytic units on a common scaffold (Himmel et al. 2010). The only cellulolytic facultative anaerobes reported to date are members of the genus Cellulomonas (Christopherson et al. 2013; Lynd et al. 2002; Stackebrandt 2006) and a few other taxa, including Actinotalea fermentans, formerly Cellulomonas fermentans (Yi et al. 2007) and Caulobacter sp. FMC1 (Song et al. 2013). Although Cellulomonas sp. are known to use a variety of soluble substrates anaer
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