1) Paper Name: Feasibility of a facile butanol bioproduction using planetary mill pretreatment
2) Authors: JH Kwon, H Kang, BI Sang, Y Kim, J Min, RJ Mitchell, JH Lee
3) Date: 28 Aug, 2015
4) Journal name: Bioresource Technology
5) Impact factor: 4,494
6) Abstract: A facile butanol bioproduction process was developed using planetary milling, and Pinus rigida wood waste as a model substrate for fermentable sugars. The use of planetary milling as the pretreatment eliminates the need for washing and transfer of the biomass prior to enzymatic hydrolysis. Moreover, using this pretreatment process resulted in the production of only 0.072 ± 0.003 g/L soluble phenolic compounds, a concentration that was not inhibitory towards Clostridium beijerinckii NCIMB 8052. As the milling was performed in a compatible buffer (50 mM acetate, pH 4.8), the enzymatic hydrolysis step was initiated by simply adding the cellulase cocktail powder directly to pretreated biomass without washing the biomass or exchanging the buffer, resulting in a glucose yield of 31 g/L (84.02%). Fermentation of the hydrolysate samples by C. beijerinckii NCIMB 8052 gave slightly better butanol yields than cultures grown in a typical lab media (P2), with final concentrations of 6.91and 6.66 g/L, respectively.
1) Paper Name: Effects of Carbon Dioxide Aerosols on the Viability of Escherichia coli during Biofilm Dispersal
2) Authors: R Singh, AK Monnappa, S Hong, RJ Mitchell, J Jang
3) Date: 8 Sept, 2015
4) Journal name: Scientific Reports
5) Impact factor: 5,578
6) Abstract: A periodic jet of carbon dioxide (CO2) aerosols is a very quick and effective mechanical technique to remove biofilms from various substrate surfaces. However, the impact of the aerosols on the viability of bacteria during treatment has never been evaluated. In this study, the effects of high-speed CO2 aerosols, a mixture of solid and gaseous CO2, on bacteria viability was studied. It was found that when CO2 aerosols were used to disperse biofilms of Escherichia coli, they led to a significant loss of viability, with approximately 50% of the dispersed bacteria killed in the process. By comparison, 75.6% of the biofilm-associated bacteria were viable when gently dispersed using Proteinase K and DNase I. Indirect proof that the aerosols are damaging the bacteria was found using a recombinant E. coli expressing the cyan fluorescent protein, as nearly half of the fluorescence was found in the supernatant after CO2 aerosol treatment, while the rest was associated with the bacterial pellet. In comparison, the supernatant fluorescence was only 9% when the enzymes were used to disperse the biofilm. As such, these CO2 aerosols not only remove biofilm-associated bacteria effectively but also significantly impact their viability by disrupting membrane integrity.
3. High-level production of violacein by the newly isolated Duganella violaceinigra str. NI28 and its impact on Staphylococcus aureus
This paper will be released soon.
1) Paper Name: High-level production of violacein by the newly isolated Duganella violaceinigra str. NI28 and its impact on Staphylococcus aureus
2) Authors: SY Choi, SY Kim, S Lyuck, SB Kim, RJ Mitchell
3) Journal name: Scientific Reports
4) Abstract: A violacein-producing bacterial strain was isolated and identified as a relative of Duganella violaceinigra YIM 31327 based upon phylogenetic analyses using the 16S rRNA, gyrB and vioA gene sequences and a fatty acid methyl ester (FAME) analysis. This new strain was designated D. violaceinigra str. NI28. Although these two strains appear related based upon these analyses, the new isolate was phenotypically different from the type strain as it grew 25% faster on nutrient media and produced 45-fold more violacein. When compared with several other violacein producing strains, including Janthinobacterium lividum, D. violaceinigra str. NI28 was the best violacein producer. For instance, the crude violacein yield with D. violaceinigra str. NI28 was 6.0 mg/OD at 24 hours, a value that was more than two-fold higher than all the other strains. Finally, the antibacterial activity of D. violaceinigra str. NI28 crude violacein was assayed using several multidrug resistant Staphylococcus aureus. Addition of 30?M crude violacein led to a 96% loss in the initial S. aureus population while the minimum inhibitory concentration was 1.8?M. Consequently, this novel isolate represents a phenotypic variant of D. violaceinigra capable of producing much greater quantities of crude violacein, an antibiotic effective against multidrug resistant S. aureus.