In the present preliminary study, we report results for the biocellulose nanofibres production by Gluconacetobacter xylinus. Production was examined by utilizing different feedstocks of single sugars and sugar mixtures with compositions similar to the acid hydrolyzates of different agriculture residues. Profiles for cell proliferation, sugar consumption, and the subsequent pH changes were thoroughly analyzed. Highest biocellulose production of 5.65 g/L was achieved in fructose medium with total sugar consumption of 95.57%. Moreover, the highest production using sugar mixtures was 5.2 g/L, which was achieved in feedstock with composition identical to the acid hydrolyzate of wheat straws. This represented the highest biocellulose yield of 17.72 g/g sugars compared with 14.77 g/g fructose. The lowest production of 1.1 and 1.75 g/L were obtained in xylose and glucose media, respectively, while sucrose and arabinose media achieved relatively higher production of 4.7 and 4.1 g/L, respectively. Deviation in pH of the fermentation broths from the optimum value of 4-5 generally had marked effect on biocellulose production with single sugars in feedstock. However, the final pH values recorded in the different sugar mixtures were approximately 3.3-3.4, which had lower effect on production hindrance. Analyzing profiles for sugars' concentrations and cell growth showed that large amount of the metabolized sugars were mainly utilized for bacterial cell growth and maintenance, rather than biocellulose production. This was clearly observed with single sugars of low production, while sugar consumption was rather utilized for biocellulose production with sugar mixtures. Results reported in this study demonstrate that agriculture residues might be used as potential feedstocks for the biocellulose nanofibres production. Not only this represents a renewable source of feedstock, but also might lead to major improvements in production if proper supplements and control were utilized in the fermentation process.
S-carvone, L-menthone, peppermint and spearmint oils were tested in vitro against Fusarium coeruleum, F. sambucinum, F. avenaceum, F. oxysporum, Alternaria solani, Rhizoctonia solani, Helminthosporium solani, Phytophthora infestans (A1 and A2 mating types), Phytophthora erythroseptica, Phoma exigua and Pythium ultimum which are causal agents of major potato storage diseases. The majority of these pathogens were completely inhibited due to pure oils, although F. sambucinum, F. avenaceum, A. solani and P. exigua were not completely inhibited by one or more pure oils. Peppermint oil was the least effective among tested oils. However, R. solani, H. solani, P. erythroseptica, and P. infestans (A1 and A2 mating types) were completely inhibited for a period of 1-18 weeks by single treatments of all four pure oils. Effects of mixtures of aluminum starch octenylsuccinate (ASOS) and L-menthol or peppermint oil on F. sambucinum and R. solani were also tested in vitro for a period of over 5 weeks. Percent inhibition of F. sambucinum by single application of mixtures of ASOS and L-menthol or peppermint oil decreased over 11-13 days after treatment, while the mixtures at the same rates consistently inhibited the growth of R. solani for over 15 days. Mixtures of 10 g of ASOS and 4 g or 8 g doses of essential oils were the most effective in inhibiting pathogens growth for periods over 13 or 20 days, respectively. The antifungal effects of essential oils and their components against all tested pathogens suggest their potential use as alternative tools for controlling potato storage diseases.
This paper investigates the bioseparation of binary protein mixtures using polystyrene based anion exchange resin. Adsorption experiments were conducted in batch mode using draft-tube internally recirculate dair lift biocontactor in comparison with the conventional shake flask batch adsorption equilibrium experiments. Binary protein mixtures contained bovine serum albumin (BSA) and bovine haemoglobin (BHb) at different initial fractions. Results from single solute adsorption experiments in biocontactor showed that both proteins were equally adsorbed onto the resin with equilibrium reached in an equal time period. This represents similar affinities towards the negatively charged resin surface, although BSA was expected to adsorb through specific forces. Adsorption results showed that BSA has hindered the BHb adsorption in the biocontactor, although adsorption of both proteins was equally hindered in the shake flasks adsorption experiments. Moreover, adsorption of BHb was inhibited up to 29% in the presence of BSA compared to the adsorption of BHb from a solution containing single solute of BHb at the same initial concentration. Similarly, the presence of BHb has hindered the adsorption of BSA by 59%. Adsorptions of both BSA and BHb from binary solution when each formed 75% initial fraction while the other protein formed the remaining 25% were relatively low with equilibrium reached in shorter time. Moreover, considerable amount of proteins remained in the solution, which demonstrates that multilayer adsorption most likely didn’t occur at the relatively small protein concentrations used in the present study. In general, the higher adsorption of BHb can also be related to the compressibility of its molecules which allowed for higher adsorption capacity. The homogeneous and lower shear environment in the airlift biocontactor compared to the other conventional batch adsorption in shake flask reduced the compressibility of BHb that caused higher BSA adsorption from binary solutions of BSA and BHb, which allowed for better bioseparation of both proteins.
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