Artificial neural network-genetic algorithm based optimization for the immobilization of cellulase on the smart polymer Eudragit L-100

Cellulase was covalently immobilized on a smart polymer, Eudragit L-100 by carbodiimide coupling. Using data of central composite design, response surface methodology (RSM) and artificial neural network (ANN) were developed to investigate the effect of pH, carbodiimide concentration, and coupling time on the activity yield of immobilized cellulase. Results showed simulation and prediction accuracy of ANN was apparently higher compared to RSM. The Maximum activity yield obtained from RSM was 57.56% at pH 5.54, carbodiimide concentration 0.32%, and coupling time 3.03 h, where the experimental value was 60.87 +/- 4.79%. Using ANN as fitness function, a maximum activity yield of 69.83% was searched by genetic algorithm at pH 5.07, carbodiimide concentration 0.36%, and Coupling time 4.10 h, where the experimental value was 66.75 +/- 5.21%. ANN gave a 9.7% increase of activity yield over RSM. After reusing immobilized cellulase for 5 cycles, the remaining productivity was over 50%. (C) 2009 Elsevier Ltd. All rights reserved

Cultivation of microalgae Chlorella zofingiensis on municipal wastewater and biogas slurry towards bioenergy

The high cost of large-scale cultivation of microalgae has limited their industrial application. This study investigated the potential use of mixed biogas slurry and municipal wastewater to cultivate microalgae. Pig biogas slurry as the sole nutrient supplement, was assessed for the cultivation of Chlorella zofingiensis in municipal wastewater. Batch culture of various ratios of pig biogas slurry and municipal wastewater were compared. The characteristics of algal growth and lipid production were analyzed, and the removal rates of nitrogen and phosphate were examined. Results indicate that 8% pig bio-gas slurry in municipal wastewater, had a significant effect on microalgal growth. C. zofingiensis, with 2.5 g L-1 biomass, 93% total nitrogen and 90% total phosphorus removal. Lipid content was improved by 8% compared to BG11 medium. These findings show that mixing pig biogas slurry and municipal wastewater, without additional nutrition sources, allows efficient cultivation of C. zofingiensis. This is of high research and industrial significance, allowing cultivation of C. zofingiensis in mixed waste culture solution without additional nutrition sources. (C) 2018, The Society for Biotechnology, Japan. All rights reserved

Evaluation of structural factors affecting high solids enzymatic saccharification of alkali-pretreated sugarcane bagasse

Filter paper and xylan were selected as model substrates simulating cellulose and hemicellulose components. Enzymatic hydrolysis of different substrates: pure filter paper, xylan added system, alkali pretreated sugarcane bagasse (SCB) were studied at varying solids loading to assess the effect of hemicellulose on substrate conversion at high solids loading. Meanwhile, hydrophilic lignin (sulfonated lignin or alkali lignin) was added to 15% (w/v) alkali-pretreated SCB hydrolysis system to investigate lignin influence on cellulose digestibility. It was found that xylan as the physical barrier had inhibitory effect on cellulose hydrolysis. Enzymatic saccharification of alkali-pretreated SCB was significantly improved by supplementing with hydrophilic lignin. The effect of lignin on substrate conversion depended not only on the hydrophilic characteristics of lignin, but also on the form of lignin present in different substrates

Metabolic changes of starch and lipid triggered by nitrogen starvation in the microalga Chlorella zofingiensis

The aim of this research was to study the metabolic changes of starch and lipid biosynthesis in the microalga Chlorella zofingiensis under nitrogen starvation in comparison to nitrogen abundant condition. C. zonfingiensis showed a rapid growth and kept stable chlorophyll content when grown in nitrogen-replete medium, while a severe inhibition of cell growth and a sharp degradation of chlorophyll occurred under nitrogen depletion. Nitrogen-replete C. zonfingiensis cells possessed basal levels of starch and lipid. Upon nitrogen starvation, both starch and lipid increased greatly within cells, but starch synthesis preceded lipid accumulation. After 2 days of stress condition, starch was partially degraded, possibly to support lipid synthesis. It was speculated that starch accumulation acted as a quick response to environmental stress, whereas lipid served as long-term energy storage. Additionally, C. zonfingiensis tends to lower the degree of unsaturation in response to nitrogen starvation which is desirable for biodiesel production. (C) 2013 Elsevier Ltd. All rights reserved

A study of CO/syngas bioconversion by Clostridium autoethanogenum with a flexible gas-cultivation system

Bioconversion of CO/syngas to produce ethanol is a novel route in bioethanol production, which can be accomplished by some acetogens. Specific culture vessels and techniques are needed to cultivate these microorganisms since they are anaerobic and substrates are gaseous. In this work, gas-sampling bag was applied as a gas-cultivation system to study CO/syngas bioconversion by Clostridium autoethanogenum and was demonstrated to be efficient because of its flexibility and excellent ability to maintain the headspace atmosphere. C autoethanogenum can use CO as the sole carbon and energy source to produce ethanol, acetate as well as CO2. In the experimental range, higher ethanol production was favored by higher yeast extract concentrations, and the maximum ethanol concentration of 3.45 g/L was obtained at 1.0 g/L of yeast extract. Study with various bottled gases showed that C. autoethanogenum preferred to use CO other than CO2 and produced the highest level of ethanol with 100% CO as the substrate. C. autoethanogenum can also utilize biomass-generated syngas (36.2% CO, 23.0% H-2, 15.4% CO2, 11.3% N-2), but the process proceeded slowly and insufficiently due to the presence of O-2 and C2H2. In our study, C. autoethanogenum showed a better performance in the bioconversion of CO to ethanol than Clostridium ljungdahlii, a strain which has been most studied, and for both strains, ethanol production was promoted by supplementing 0.5 g/L of acetate. (C) 2017 Elsevier Inc. All rights reserved

Medium optimization for ethanol production with Clostridium autoethanogenum with carbon monoxide as sole carbon source

Plackett-Burman and central composite designs were applied to optimize the medium for ethanol production by Clostridium autoethanogenum with CO as sole carbon source, and a medium containing (g/L): NaCl 1.0, KH(2)PO(4) 0.1, CaCl(2) 0.02, yeast extract 0.15. MgSO(4) 0.116, NH(4)Cl 1.694 and pH 4.74 was found optimal. The optimum ethanol yields predicted by response surface methodology (RSM) and an artificial neural network-genetic algorithm (ANN-GA) were 247.48 and 261.48 mg/L, respectively. These values are similar to those obtained experimentally under the optimal conditions suggested by the statistical methods (254.26 and 259.64 mg/L). The fitness of the ANN-GA model was higher than that of the RSM model. The yields obtained substantially exceed those previously reported (60-70 mg/L) with this organism. (C) 2010 Elsevier Ltd. All rights reserved

Enhanced isolation of lipids from microalgal biomass with high water content for biodiesel production

In present study, lipids were extracted from unbroken microalga Chlorella vulgaris with high water content (50% microalgal solution) through three-phase partitioning (TPP). The method was found to extract around 15.9% of total lipid transformable to methyl esters (LTMEs) from unbroken microalgal cells which is two times of Bligh and Dyer method. We investigated the effects of various parameters on TPP performance and were optimised through response surface methodology. The results indicated that incubation duration, temperature and extraction time were positively correlated with LTME extraction efficiency. The optimum temperature was 60 degrees C, incubation duration was 120 min, extraction time was 60 min, ratio of solvent to DKP was 1: 1. The FAME yield was calculated as 12.05% and major fatty acids together accounted for 71.33% which indicated the great potential of the proposed lipid extraction procedure for microalga-based biodiesel production

Enhancement of high-solids enzymatic hydrolysis efficiency of alkali pretreated sugarcane bagasse at low cellulase dosage by fed-batch strategy based on optimized accessory enzymes and additives

Obtaining higher amount of final sugars with low cellulase dosage has great economic benefits for the industrial biorefinery of lignocellulosic biomass. The optimization of accessory enzymes and additives were performed using single factor and orthogonal experiment firstly, after that, fed-batch strategy was applied to enhance the high-solids enzymatic hydrolysis efficiency of alkali pretreated sugarcane bagasse (SCB). A novel enzymatic hydrolysis procedure with 22% (w/v) substrate content and cellulase dosage of only 4 FPU/g dry biomass (DM) was developed, after digested for 48 h, the achieved glucose titer, yield and productivity were 122 g/L, 80% and 2.54 g L-1 h(-1), respectively. Results obtained in this study indicated a potential finding for the industrial application of lignocellulosic biomass