Fungal Invertase as Aid for Production of Ethanol from Sugarcane Bagasse

Bio-ethanol production from waste biomass of Pogonatherum crinitum phytoremediator: an eco-friendly strategy for renewable energy

In this study, we have described three steps to produce ethanol from Pogonatherum crinitum, which was derived after the treatment of textile wastewater. (a) Production of biomass: biomass samples collected from a hydroponic P. crinitum phytoreactor treating dye textile effluents and augmented with Ca-alginate immobilized growth-promoting bacterium, Bacillus pumilus strain PgJ (consortium phytoreactor), and waste sorghum husks were collected and dried. Compositional analysis of biomass (consortium phytoreactor) showed that the concentration of cellulose, hemicelluloses and lignin was 42, 30 and 17%, respectively, whereas the biomass samples without the growth-promoting bacterium (normal phytoreactor) was slightly lower, 40, 29 and 16%, respectively. (b) Hydrolysate (sugar) production: a crude sample of the fungus, Phanerochaete chrysosporium containing hydrolytic enzymes such as endoglucanase (53.25 U/ml), exoglucanase (8.38 U/ml), glucoamylase (115.04 U/ml), xylanase (83.88 U/ml), LiP (0.972 U/ml) and MnP (0.459 U/ml) was obtained, and added to consortium, normal and control phytoreactor derived biomass supplemented with Tween-20 (0.2% v/v). The hydrolysate of biomass from consortium phytoreactor produced maximum reducing sugar (0.93 g/l) than hydrolysates of normal phytoreactor biomass (0.82 g/l) and control phytoreactor biomass (0.79 g/l). FTIR and XRD analysis confirmed structural changes in treated biomass. (c) Ethanol production: the bioethanol produced from enzymatic hydrolysates of waste biomass of consortium and normal phytoreactor using Saccharomyces cerevisiae (KCTC 7296) was 42.2 and 39.4 g/l, respectively, while control phytoreactor biomass hydrolysate showed only 25.5 g/l. Thus, the amalgamation of phytoremediation and bioethanol production can be the truly environment-friendly way to eliminate the problem of textile dye along with bioenergy generation.

Cloning and expression of Saccharomyces cerevisiae SUC2 gene in yeast platform and characterization of recombinant enzyme biochemical properties

Invertase (EC.3.2.1.26) catalyzes the hydrolysis of sucrose to an equimolar mixture of D-glucose and D-fructose which is of interest for various industrial applications. In this research, Saccharomyces cerevisiae invertase gene (SUC2) was optimized based on Pichia pastoris codon preference. The synthetic gene was introduced into the methylotrophic yeast Pichia pastoris under the control of the inducible AOX1 promoter. High level of the extracellular recombinant invertase (R-inv) production was achieved via methanol induction for 4 days and purified by His-Tag affinity chromatography which appeared to be a mixture of glycosylated proteins with various sizes of 85-95 kDa on SDS-PAGE. Deglycosylation of the proteins by Endo-H resulted in the proteins with average molecular weight of 60 kDa. The purified recombinant invertase biochemical properties and kinetic parameters determined a pH and temperature optimum at 4.8 and 60 °C, respectively, which in comparison with native S. cerevisiae invertase, thermal stability of recombinant invertase is highly increased in different heating treatment experiments. The purification of recombinant invertase resulted in an enzyme with specific activity of 178.56 U/mg with 3.83-fold of purification and the kinetic constants for enzyme were Km value of 19 mM and Vmax value of 300 μmol min-1 mg-1 With kinetic efficiency (Kcat/Km) of 13.15 s-1 mmol-1 it can be concluded that recombinant P. pastoris invertase can be more effective for industrial quality criteria. We conclude that recombinant P. pastoris enzyme with broad pH stability, substrate specificity and proper thermal stability can fulfil a series of predefined industrial quality criteria to be used in food, pharmaceutical and bio ethanol production industries.

Impact of changes in fermentation time, volume of yeast, and mass of plantain pseudo-stem substrate on the simultaneous saccharification and fermentation potentials of African land snail digestive juice and yeast

This study was carried out to investigate the effect of variations in mass of plantain pseudo-stem waste, volume of yeast used, and fermentation time on the product yield resulting from simultaneous saccharification and fermentation using digestive juice of African land snail and yeast. The experiment was divided into three stages which included a total of fifty seven (57) experimental setups containing sixteen (19) different combinations of the varied substrates. The results show that by varying the mass of plantain pseudo-stem waste, the production of ethanol was optimized at a mass of 250 g, which yielded 125.6 ml ± 3.5 of distillate and a percentage ethanol composition of 25.0 ± 3.6. While varying the volume of yeast used between 50 and 250 ml, with 250 g of plantain pseudo-stem waste, 250 ml of snail digestive juice and 4 g garlic for 24 h, acetic acid was detected in the setup containing 200 ml of yeast, but was not detected in similar experimental setups containing 6 g garlic. The optimum ethanol production while varying the volume of yeast slurry was recorded to be 182.3 ml ± 4.9 of distillate with 28.0% ± 1.0 ethanol composition. Variations in fermentation periods had the greatest impact on the percentage composition of ethanol and the volume of ethanol produced showing the best fermentation period for obtaining optimal ethanol production to be at 96 h. These findings show that the best specifications for the optimum production of ethanol from a 250 g of plantain pseudo-stem waste using 250 ml snail digestive, are 200 ml of yeast slurry, 6 g of garlic to ferment for a period of 96 h.

Catalytic efficiency and thermostability improvement of Suc2 invertase through rational site-directed mutagenesis

Engineering of invertases has come to attention because of increasing demand for possible applications of invertases in various industrial processes. Due to the known physicochemical properties, invertases from micro-organisms such as Saccharomyces cerevisiae carrying SUC2 gene are considered as primary models. To improve thermostability and catalytic efficiency of SUC2 invertase (SInv), six influential residues with Relative Solvent Accessibility<5% were selected through multiple-sequence alignments, molecular modelling, structural and computational analyses. Consequently, SInv and 5 mutants including three mutants with single point substitution [Mut1=P152V, Mut2=S85V and Mut3=K153F)], one mutant with two points [Mut4=S305V-N463V] and one mutant with three points [Mut5=S85V-K153F-T271V] were developed via site-directed mutagenesis and produced using Pichia pastoris as the host. Physicochemical studies on these enzymes indicated that the selected amino acids which were located in the active site region mainly influenced catalytic efficiency. The best improvement belonged to Mut1 (54% increase in K_cat/K_m) and Mut3 exhibited the worst effect (90% increase in K_m). These results suggest that Pro152 and Lys153 play key role in preparation of the right substrate lodging in the active site of SInv. The best thermostability improvement (16%) was observed for Mut4 in which two hydrophilic residues located on the loops, far from the active site, were replaced by Valines. These results suggest that tactful simultaneous substitution of influential hydrophilic residues in both active site region and peripheral loops with hydrophobic amino acids could result in more thermostable invertases with enhanced catalytic efficiency.

Optimization of cellulase production by Enhydrobacter sp. ACCA2 and its application in biomass saccharification

Cellulase finds use in saccharification of lignocellulosic agroresidues to fermentable sugars which can be used for production of commercially important metabolites. This study reports endoglucanase (CMCase) production by Enhydrobacter sp. ACCA2. The CMCase activity of the strain ACCA2 was successively improved by optimization of range of physical and nutritional parameter in a set of non-statistical and statistical experiments. Initial non-statistical selection of carbon source, incubation time, temperature and pH resulted in 1.07 fold increase of CMCase activity. In a subsequent statistical method, response surface methodology, optimization of medium components such as carboxymethylcellulose, peptone, NaCl, MgSO4, K2HPO4, and (NH4)2SO4 yielded further increase up to 2.39 fold CMCase activity. The cellulolytic potential was evaluated in biomass saccharification with different plant materials and the results revealed that the enzyme produced by strain may have significant commercial values for industrial saccharification process. Moreover, this is the first report of cellulase production by an Enhydrobacter spp.