Isobutanol and 3-methyl-1-butanol production by saccharomyces cerevisiae in aerobic condition

Alternative fuels from renewable sources are receiving public and scientific attention due to continuous depletion of petroleum fuel-reserves and environmental problem such as global warming and climate change. Higher alcohols (C3-C5) possess many advantages thus become suitable candidate in replacing gasoline as transprtation fuel. This paper investigates the production of isobutanol and 3-methyl-1-butanol as well as the toxicity of these alcohols towards Saccharomyces cerevisiae. This yeast was able to produce both alcohols with the highest concentration of 92 mg/ L (isobutanol) and 245 mg/L (3-methyl-1-butanol). Saccharomyces cerevisiae was capable to grow in more than 2% isobutanol but unable in concentration of 3-methyl-1-butanol higher than 1%

A Short Review on Recent Development of Laccase Immobilization on Different Support Materials

Laccase is a bio catalytic agent and multi-copper enzyme containing oxidases that are potentially great for oxidizing large number of phenolic and non-phenolic compounds. However, drawbacks do arise when laccase use in large scale; low in stability, high production cost, non-reusability, sensitive towards denaturing and poor storage ability of free enzymes. These problems lead to the progress in laccase immobilization in order to facilitate the efficient recovery and re-use of the enzyme, thus enabling cost-effective in continuous processes. Apart from discussing on different methods in laccase immobilization such as entrapment, encapsulation and cross-linking in general, we have reviewed a recent development in laccase immobilization on different supports or carriers binding (natural and synthetic). Future works are recommended to focus on innovative strategies on the modified supports to improve the enzyme immobilization as well as sensible entrapment techniques for industrial applications

Introduction to Enzyme Immobilization

Recent advances in biotechnology and bioengineering have shown an increasing trend towards the development of environmentally friendly, safe and sustainable bioprocesses using enzymes. The excellent selectivity, specificity and catalytic performance have made enzymes robust biocatalysts with a wide range of applications in biomedicine, biosensing, and biocatalysis (Bilal et al., 2021). Due to the low use of chemicals and the absence of hazardous metabolites/byproducts, the use of biocatalysts is expected to facilitate environmentally friendly processes. In addition, there is a recurring obstacle in the various industries where biocatalysis can be used: the application of enzyme catalysis in chemical processes is limited by the lack of stability of enzymes at high temperatures or in turbulent flow regimes, as well as in potentially toxic solvents (Chapman et al., 2018

Screening of factors influencing exo-polygalacturonase production by Aspergillus niger ATCC 120120 using two-level fractional factorial design

Exo-polygalacturonase was produced by Aspergillus niger ATCC 120120 in a solid-state fermentation using Nephrolepis biserrata leaves. Factors affecting the production of exo-polygalacturonase were determined using a two-level fractional factorial design. The screening process for six factors; pH, incubation time, temperature, pectin concentration, inoculum size and moisture content, that influence the production of exo-polygalacturonase by A. niger was performed. The result of variance analysis (ANOVA) suggested that there were four statistically significant (P < 0.005) factors in the production of exo-polygalacturonase by A. niger. These factors were incubation time, temperature, pectin concentration and moisture content. The statistical analysis shows that the linear mathematical model is significant with coefficient of determination (R2) value of 0.9711. The optimum production of exo-polygalacturonase obtained using the model in this study was at 40.00 U/g

Optimization and characterization of exo-polygalacturonase by Aspergillus niger cultured via solid state fermentation

Polygalacturonases represent an important member of pectinases group of enzymes with immense industrial applications. The activity of exo-polygalacturonase produced by Aspergillus niger was studied in solid state fermentation (SSF) using Nephrolepis biserrata leaves as substrate. Central composite design (CCD) was used to optimize four significant variables resulted from the screening process that has been initially analyzed for the production of exo-polygalacturonase which are incubation time, temperature, concentration of pectin and moisture content. The optimum exo-polygalacturonase production obtained was 54.64 U/g at 120 hours of incubation time, temperature at 340C, 5.0 g/L of pectin concentration and 75.26% of moisture content. For partial characterization of exo-polygalacturonase, the optimum temperature and pH were obtained at 50°C and pH 4.0, respectively. SDS-PAGE analysis showed that molecular weight of exo-polygalacturonase were 35 and 71 kDa. This study has revealed a significant production of exo-polygalacturonase by A. niger under SSF using cheap and easily available substrate and thus could found immense potential application in industrial sectors and biotechnology

Enhancement of isobutanol and 3-methyl-1-butanol production yields in saccharomyces cerevisiae without genetic modification

Bio-based fuel produced from the renewable resources is efficiently overcome the shortcomings of fossil fuels. Several factors such as the increasing awareness on environmental problems, fossil fuel prices and the sustainability of energy has encouraged the initiative in finding another source of transportation fuels. Higher alcohols have proved to be a better candidate to replace gasoline as vehicle fuel due to characteristics of higher energy content, low solubility in water, lower vapor pressure and higher blending ability with gasoline. Biologically, isobutanol and 3-methyl-1-butanol are produced through the fermentation of renewable feedstock with microorganism. Saccharomyces cerevisiae is known to be able to produce isobutanol and 3-methyl-1-butanol titers naturally without heterologous pathways. However, the production of these alcohols by Saccharomyces cerevisiae is only in a small quantity, thus several efforts in enhancing the isobutanol and 3-methyl-1-butanol yields have been conducted. In this study, the amino acids (valine and leucine) and amino acid precursor (2-ketoisovalerate) were added into the fermentation medium prior to the fermentation. The results obtained show that the supplementation of 2-ketoisovalerate and leucine individually into the fermentation broth leads to the increased in isobutanol and 3-methyl-1-butanol titers by 3.3 folds and 1.9 folds, respectively. The combination of 2-ketoisovalerate and valine increased the isobutanol yield by 4.3 folds while the 3-methyl-1-butanol was increased by 2.5 folds when supplemented with 2-ketoisovalerate and leucine. These results portray that the isobutanol and 3-methyl-1-butanol titers can be improved by manipulating several factors which is important for future production of higher alcohols

Screening of factors influencing Pectin Extraction of Pomelo peels using 2-Level Factorial Design

Abstract. A study was conducted to vary the parameters affecting the extraction of pectin from pomelo peels (Citrus maxima) using a 2-level factorial design (2LFD). Experimental design was carried out to screen for significant environmental factors for extraction results. The factors involved consisted of pH, temperature and extraction time. The results of the variance analysis (ANOVA) found three main factors that had a statistically significant effect on the results of pectin extraction, namely pH, temperature and extraction time. The following important factors are the interaction factors between pH and temperature, the interaction between temperature and extraction time, the interaction between pH and extraction time, the interaction between temperature and extraction time. Statistical analysis shows that the linear model is significant with R2 value of 0.9715. It was found that pH, temperature and extraction time are the most important parameters that affect the results of pomelo peels pectin extraction

Optimization of pectin extraction from kepok banana peels (musa paradisiaca) using surface response methodology

Abstract:The experimental design in this study was used to optimize the results of extracting pectin from kepok banana peels by surface method. The model for predicting and optimizing the process of extracting kepok banana pectin consists of 4 axillary points, 4 factorial points, and 5 middle titlication replications using a central commision design (CCD) with DX6.0.4 software. The independent variables used in the optimization of the extraction results of kepok banana pectin are pH and temperature, where the pH is between 1.5 - 2.5 and temperatures are 60°C-100°C and the combination of independent and bound variables (extraction time). The results of pectin extract ranged from 5.79% to 22.57% (b / b, based on the dry weight of kepok banana peel). The variables of pH and temperature, the interaction between pH and temperature, and the interaction between extraction time and pH significantly influence. The optimum conditions for extraction of pectin are estimated at pH (2.5) and temperature (100°C). In optimal conditions, the actual pectin yield is 22.57%, which is below the estimated extraction condition of 21.286%. Analysis of variance, adj R2 and R2, model lack of fit test, and p value statistically indicate that the model is adequate in representing experimental data. The effect of pH and extraction temperature was very significant (P <0.001) on the extraction results of kepok banana peel pectin. This shows that these two variables are very important in the process of extracting kepok banana peel, where the R2 value is 96.01%

Optimization of process parameters for pilot-scale liquid-state bioconversion of sewage sludge by mixed fungal inoculation

Liquid-state bioconversion (LSB) technique has great potential for application in bioremediation of sewage sludge. The purpose of this study is to determine the optimum level of LSB process of sewage sludge treatment by mixed fungal (Aspergillus niger and Penicillium corylophilum) inoculation in a pilot-scale bioreactor. The optimization of process factors was investigated using response surface methodology based on Box–Behnken design considering hydraulic retention time (HRT) and substrate influent concentration (S0) on nine responses for optimizing and fitted to the regression model. The optimum region was successfully depicted by optimized conditions, which was identified as the best fit for convenient multiple responses. The results from process verification were in close agreement with those obtained through predictions. Considering five runs of different conditions of HRT (low, medium and high 3.62, 6.13 and 8.27 days, respectively) with the range of S0 value (the highest 12.56 and the lowest 7.85 g L−1), it was monitored as the lower HRT was considered as the best option because it required minimum days of treatment than the others with influent concentration around 10 g L−1. Therefore, optimum process factors of 3.62 days for HRT and 10.12 g L−1 for S0 were identified as the best fit for LSB process and its performance was deviated by less than 5% in most of the cases compared to the predicted values. The recorded optimized results address a dynamic development in commercial-scale biological treatment of wastewater for safe and environment-friendly disposal in near future

Process optimisation of effective partition constant in coconut water via progressive freeze concentration

Concentration technique via progressive freeze concentration was applied to increase the concentration of coconut water for commercialisation. The process will eliminate portion of water from coconut water and retain pure nutritional compound with high sugar content. To obtain the optimum condition, which is the objective of this study, optimisation process was conducted using Response Surface Methodology (RSM) through STATISTICA Software. RSM was utilised to optimise the process parameters for effective partition constant (K) in progressive freeze concentration (PFC) of the coconut water. The effects of circulation flowrate, circulation time, initial solution concentration and coolant temperature on effective partition constant were observed. Results show that the data adequately fit the second-order polynomial model. The linear and quadratic independent variables, circulation flowrate, circulation time, initial concentration and coolant temperature have significant effects as well as interactions on the effective partition constant. It was observed that the optimum process parameters within the experimental range for the best K would be with circulation flowrate of 3,400 mL/min, circulation time of 23 min, initial concentration of 3.4 % Brix and coolant temperature of -7 °C. Under these conditions, the K can be enhanced up to 0.3