Amizon Azizan

Liquid films on shake flask walls explain increasing maximum oxygen transfer capacities with elevating viscosity

In biotechnological screening and production, oxygen supply is a crucial parameter. Even though oxygen transfer is well documented for viscous cultivations in stirred tanks, little is known about the gas/liquid oxygen transfer in shake flask cultures that become increasingly viscous during cultivation. Especially the oxygen transfer into the liquid film, adhering on the shake flask wall, has not yet been described for such cultivations. In this study, the oxygen transfer of chemical and microbial model experiments was measured and the suitability of the widely applied film theory of Higbie was studied. With numerical simulations of Ficks law of diffusion, it was demonstrated that Higbies film theory does not apply for cultivations which occur at viscosities up to 10 mPa s. For the first time, it was experimentally shown that the maximum oxygen transfer capacity OTRmax increases in shake flasks when viscosity is increased from 1 to 10 mPa s, leading to an improved oxygen supply for microorganisms. Additionally, the OTRmax does not significantly undermatch the OTRmax at waterlike viscosities, even at elevated viscosities of up to 80 mPa s. In this range, a shake flask is a somehow self‐regulating system with respect to oxygen supply. This is in contrary to stirred tanks, where the oxygen supply is steadily reduced to only 5% at 80 mPa s. Since, the liquid film formation at shake flask walls inherently promotes the oxygen supply at moderate and at elevated viscosities, these results have significant implications for scale‐up. Biotechnol. Bioeng. 2014;111: 295–308.

Mechanical pretreatment of lignocellulosic biomass for biofuel production

Lignocellulosic biomass (LB) sources which are readily available in abundance are widely considered as a potential future sustainable raw materials for biofuel production. Typically, biofuel production involved several chemical and mechanical steps consisting of pretreatment, hydrolysis, fermentation and separation. The pretreatment step is considered as one of the most vital part of the whole processing scheme due to the impact it had on the efficiency of the subsequent processing steps. In this study we reviewed the mechanical pretreatment of LB focusing mainly on the size reduction technique by grinding process. Grinding is one of the proven preliminary pretreatment techniques employed in biomass conversion to liquid biofuel. However, this technique is known to be costly due to high energy consumption. In view of this, an efficient and cost effective pretreatment technology is required in order for the biofuel to be produced at a competitive level. At the same time, the impact on environment caused by the conventional pretreatment processes can be minimized. Thus, a new combined chemical-mechanical pretreatment is considered whereby a green ionic liquid (IL) solvent is introduced.

Biomaterials Availability: Potential for Bioethanol Production

Over the last decade, there has been increasing research interest in the value of biosourced materials from lignocellulosic biomass. Abundant sources of lignocellulosic biomass such as palm, napier grass, luceana tree, urban waste, municipal solid waste, agricultural waste and other waste have the potential to become a sustainable source of biofuel. In Malaysia, dissolution of cellulose from palm biomass to produce ethanol as future biofuels is very promising since palm residues from palm industry are highly abundant. In addition, cellulose contents in palm wastes or residues are relatively high for instance from empty fruit bunch or palm trunk. An efficient pretreatment is highly required prior to processes which convert the lignocellulosic palm biomass to bioethanol. The kinds of processes needed nowadays are called as green technology based techniques which are environmental friendly. Various solvents have been applied to dissolve cellulose including various types of ionic liquid as well. Previously, other method such as acid hydrolysis pretreatment process cause many drawbacks due to their low rates of hydrolysis and extreme acidic conditions. The dissolution process of the lignocellulosic biomass with ionic liquids is at its better advantage due to better dissolution as compared to by using organic or inorganic solvents. Therefore, at the moment, ionic liquid is becoming more preferable in dissolving the lignocellulosic biomass or any palm residues for instance.

Biogrowth of Escherichia coli in Bio-Ionic Media

The impact of development of ionic liquids (ILs) in biochemical appliances has attracted attention from many researchers to further investigate on the potential of ILs. Use of ILs has provided an effective alternative in the conversion of source of carbohydrate in woody plant into fermentable sugar for ethanol production. To investigate how the presence of ILs affects the fermentation process, fermentation by using E. coli were conducted in different fermentation conditions with the presence of ILs. The purpose of this research is to investigate microbial growth under the presence of ILs with various parameters. Ability of E. coli to grow in facultative condition has made these bacteria suitable for this research. In this research, the growths of E. coli in the presence of ILs were observed by shaken culture method for 24 hours. The E. coli was tested to grow in 5 % v/v [0.005, 20 % v/v [0.02, and 50 % v/v [0.05 of IL concentration ratios. The three types of ILs used for this research were 1-Ethyl-3-methylimidazolium Acetate [EMIM][A, 1-Butyl-3-methylimidazolium Chloride [BMIM][Cl] and 1-Allyl-3-methylimidazolium Chloride [AMIM][Cl]. The growth patterns of E. coli were also observed during the fermentation with shaking frequency of 250 rpm, 300 rpm and 350 rpm.

Imidazolium-Based Ionic Liquid Dissolution Influence on Crystallinity of Oil Palm Frond, Oil Palm Trunk and Elephant Grass Lignocellulosic Biomass

Ionic liquid (IL) has been shown to affect cellulose crystalline structure in lignocellulosic biomass (LB) during pretreatment. This research was carried out with two different experimental design involving IL to observe the effect of dissolution in IL on: (A) the crystallinity of cellulose and (B) the dissolution efficiency of LB. For experiment A, the types of IL used in this research were 1-ethyl-3-methylimidazolium Acetate [EMI[A, 1-allyl-3-methylimidazolium Chloride [AMI[C, 1-butyl-3-methylimidazolium Chloride [BMI[C and 1-ethyl-3-methylimidazolium Chloride [EMI[C. The crystallinity degree of LB was investigated before and after pretreatment with IL. The microcrystalline cellulose (MCC) was used as the simulated LB (cellulose content) was dissolved in IL and the crystallinity after the dissolution was analyzed. The temperature (70°C, 80°C, 90°C, 99°C) and concentration ratio of IL with volume/volume (v/v: 10%, 25%, 50%) were varied while the dissolution time remained constant. The crystallinity was analyzed by using Fourier Transform Infrared Spectroscopy (FTIR). The results showed that the dissolution temperature and IL concentration ratio affects the intensity of the FTIR peaks. In experiment B, the dissolution of LB with 1-butyl-3-methylimidazolium Chloride [BMI[C and 1-Ethyl-3-methylimidazolium Chloride [EMI[C as ILs were investigated. Four types of LB involved were Elaeis guineensis species of Oil Palm Trunk (OPT) and Oil Palm Frond (OPF) and Pennisetum purpureum species (elephant grass) originated from Taiwan and India. From the results obtained, the [BMI[C gave better dissolution to biomass.