Nor Aini Abdul Rahman

Saccharification of rice straw by cellulase from a local Trichoderma harzianum SNRS3 for biobutanol production

BackgroundRice straw has shown to be a promising agricultural by-product in the bioconversion of biomass to value-added products. Hydrolysis of cellulose, a main constituent of lignocellulosic biomass, is a requirement for fermentable sugar production and its subsequent bioconversion to biofuels such as biobutanol. The high cost of commercial enzymes is a major impediment to the industrial application of cellulases. Therefore, the use of local microbial enzymes has been suggested. Trichoderma harzianum strains are potential CMCase and β-glucosidase producers. However, few researches have been reported on cellulase production by T. harzianum and the subsequent use of the crude cellulase for cellulose enzymatic hydrolysis. For cellulose hydrolysis to be efficiently performed, the presence of the whole set of cellulase components including exoglucanase, endoglucanase, and β-glucosidase at a considerable concentration is required. Biomass recalcitrance is also a bottleneck in the bioconversion of agricultural residues to value-added products. An effective pretreatment could be of central significance in the bioconversion of biomass to biofuels.ResultsRice straw pretreated using various concentrations of NaOH was subjected to enzymatic hydrolysis. The saccharification of rice straw pretreated with 2% (w/v) NaOH using crude cellulase from local T. harzianum SNRS3 resulted in the production of 29.87 g/L reducing sugar and a yield of 0.6 g/g substrate. The use of rice straw hydrolysate as carbon source for biobutanol fermentation by Clostridium acetobutylicum ATCC 824 resulted in an ABE yield, ABE productivity, and biobutanol yield of 0.27 g/g glucose, 0.04 g/L/h and 0.16 g/g glucose, respectively. As a potential β-glucosidase producer, T. harzianum SNRS3 used in this study was able to produce β-glucosidase at the activity of 173.71 U/g substrate. However, for cellulose hydrolysis to be efficient, Filter Paper Activity at a considerable concentration is also required to initiate the hydrolytic reaction. According to the results of our study, FPase is a major component of cellulose hydrolytic enzyme complex system and the reducing sugar rate-limiting enzyme.ConclusionOur study revealed that rice straw hydrolysate served as a potential substrate for biobutanol production and FPase is a rate-limiting enzyme in saccharification.

Determination of optimum harvest maturity and physico‐chemical quality of Rastali banana (Musa AAB Rastali) during fruit ripening

BACKGROUND A series of physico-chemical quality (peel and pulp colours, pulp firmness, fruit pH, sugars and acids content, respiration rate and ethylene production) were conducted to study the optimum harvest periods (either week 11 or week 12 after emergence of the first hand) of Rastali banana (Musa AAB Rastali) based on the fruit quality during ripening. RESULT Rastali banana fruit exhibited a climacteric rise with the peaks of both CO(2) and ethylene production occurring simultaneously at day 3 after ripening was initiated and declined at day 5 when fruits entered the senescence stage. De-greening was observed in both of the harvesting weeks with peel turned from green to yellow, tissue softening, and fruits became more acidic and sweeter as ripening progressed. Sucrose, fructose and glucose were the main sugars found while malic, citric and succinic acids were the main organic acids found in the fruit. CONCLUSION Rastali banana harvested at weeks 11 and 12 can be considered as commercial harvest period when the fruits have developed good organoleptic and quality attributes during ripening. However, Rastali banana fruit at more mature stage of harvest maturity taste slightly sweeter and softer with higher ethylene production which also means the fruits may undergo senescence faster than fruit harvested at week 11.

Statistical optimization of biohydrogen production from palm oil mill effluent by natural microflora.

In this study, palm oil mill effluent (POME) was used as the substrate for biohydrogen production. Heat-treated POME sludge acclimated with POME incubated at 37°C for 24 hours was used as seed culture. Preliminary screening on the effects of inocula sizes, heat treatment, substrate concentration and pH of incubation by using a factorial design (FD) were conducted under mesophilic condition (37°C) using a serum vial (160 mL). The experimental results from two-level FD showed that pH and Chemical Oxygen Demand (COD) of POME significantly affected biohydrogen production. Op- timizations of the specific hydrogen production (Ps) and the hydrogen production rate (Rm) were achieved by using a cen- tral composite design (CCD). The maximum Ps of 272 mL H2/g carbohydrate was obtained under optimum conditions of pH 5.75 and substrate concentration of 80 g/L. The maximum Rm of 98 mL H2/h was calculated under the optimum condi- tions of pH 5.98 and substrate concentration of 80 g/L. The optimized conditions obtained were subjected to a confirma- tion run and it showed reproducible data with a Ps of 226 mL H2/g carbohydrate and Rm of 72 mL H2/h.

Streptomyces ambofaciens S2 - A Potential Biological Control Agent forColletotrichum gleosporioides the Causal Agent for Anthracnose in RedChilli Fruits

Streptomycetes ambofaciens S2 was chosen to study its ability to control Colletotrichum gloeosporioides in chilli fruits. Soil samples were collected from Malaysia Agriculture Research Development Institute (MARDI) Pontain Research Station in Johor Darul Takzim, Malaysia. Streptomyces were later isolated from the soil samples and subjected to antifungal screening, metabolites characterization and in vivo testing of the potential microbes. In this study, 110 isolates of streptomycetes were successfully isolated from peat soil samples collected from Malaysia Agriculture Research Development Institute (MARDI) Pontain Research Station in Johor Darul Takzim, Malaysia. Screening for antifungal activity showed that 10 isolates of streptomycetes gave antifungal inhibition zone of 8-16 mm separately. Streptomyces ambofaciens S2 was later chosen for further testing based on the widest antifungal inhibition zone exhibited (16 mm). Characterization of S. ambofaciens S2 using both light microscope and scanning electron microscope showed that, S. ambofaciens S2 spores appeared to be rough while the spore chain arrangement was long and spiral. In vivo testing on S. ambofaciens S2, showed that C. gleosporioides infected chilli fruits sprayed with S. ambofacines S2 extract did not showed any sign of infection when compared with chilli fruits sprayed with ethyl acetate. Minimal inhibition concentration (MIC) performed on S. ambofaciens S2 against C. gleosporioides was observed to be 0.8125 mg/ml. The test conducted showed that S. ambofaciens S2 maybe an alternative biopesticide for control of C. gleosporioides. However, further tests should be in place to ascertain the viability and toxicity of the extract towards human health and environment.

Potential of bioethanol production from Nypa fruticans sap by a newly isolated yeast Lachancea fermentati

Four isolated yeast strains from nypa sap: Saccharomyces cerevisiae, Candida tropicalis, Candida parapsilosis, and Lachancea fermentati were screened for their abilities to produce ethanol from Nypa fruticans sap. Fermentation was carried out in shake flasks at 30 °C, 200 rpm utilizing 50 g/l sugar of nypa sap. L. fermentati produced the highest ethanol level (18.7 g/l) with 75% efficiency, thus it was selected for further process optimization. Aiming to obtain high yields of ethanol, orthogonal experiments of ethanol fermentation from nypa sap using L. fermentati were carried out in 250 ml shake flasks to investigate the effects of the main parameters: temperature, pH, substrate concentration, and fermentation time. The results showed that the optimum conditions for bioethanol production were temperature of 30 °C, pH 5.4, substrate concentration of 110 g/l, and fermentation time of 20 h. The model predicted that the maximum concentration of ethanol produced under the above optimum conditions was 46.83 g/...

Effects of glucose, ethanol and acetic acid on regulation of ADH2 gene from Lachancea fermentati

Background. Not all yeast alcohol dehydrogenase 2 (ADH2) are repressed by glucose, as reported in Saccharomyces cerevisiae. Pichia stipitis ADH2 is regulated by oxygen instead of glucose, whereas Kluyveromyces marxianus ADH2 is regulated by neither glucose nor ethanol. For this reason, ADH2 regulation of yeasts may be species dependent, leading to a different type of expression and fermentation efficiency. Lachancea fermentati is a highly efficient ethanol producer, fast-growing cells and adapted to fermentation-related stresses such as ethanol and organic acid, but the metabolic information regarding the regulation of glucose and ethanol production is still lacking. Methods. Our investigation started with the stimulation of ADH2 activity from S. cerevisiae and L. fermentati by glucose and ethanol induction in a glucose-repressed medium. The study also embarked on the retrospective analysis of ADH2 genomic and protein level through direct sequencing and sites identification. Based on the sequence generated, we demonstrated ADH2 gene expression highlighting the conserved NAD(P)-binding domain in the context of glucose fermentation and ethanol production. Results. An increase of ADH2 activity was observed in starved L. fermentati (LfeADH2) and S. cerevisiae (SceADH2) in response to 2% (w/v) glucose induction. These suggest that in the presence of glucose, ADH2 activity was activated instead of being repressed. An induction of 0.5% (v/v) ethanol also increased LfeADH2 activity, promoting ethanol resistance, whereas accumulating acetic acid at a later stage of fermentation stimulated ADH2 activity and enhanced glucose consumption rates. The lack in upper stream activating sequence (UAS) and TATA elements hindered the possibility of Adr1 binding to LfeADH2. Transcription factors such as SP1 and RAP1 observed in LfeADH2 sequence have been implicated in the regulation of many genes including ADH2. In glucose fermentation, L. fermentati exhibited a bell-shaped ADH2 expression, showing the highest expression when glucose was depleted and ethanol-acetic acid was increased. Meanwhile, S. cerevisiae showed a constitutive ADH2 expression throughout the fermentation process. Discussion. ADH2 expression in L. fermentati may be subjected to changes in the presence of non-fermentative carbon source. The nucleotide sequence showed that ADH2 transcription could be influenced by other transcription genes of glycolysis oriented due to the lack of specific activation sites for Adr1. Our study suggests that if Adr1 is not capable of promoting LfeADH2 activation, the transcription can be controlled by Rap1 and Sp1 due to their inherent roles. Therefore in future, it is interesting to observe ADH2 gene being highly regulated by these potential transcription factors and functioned as a promoter for yeast under high volume of ethanol and organic acids.

Direct utilization of kitchen waste for bioethanol production by separate hydrolysis and fermentation (SHF) using locally isolated yeast

ABSTRACT Kitchen wastes containing high amounts of carbohydrates have potential as low-cost substrates for fermentable sugar production. In this study, enzymatic saccharification of kitchen waste was carried out. Response surface methodology (RSM) was applied to optimize the enzymatic saccharification conditions of kitchen waste. This paper presents analysis of RSM in a predictive model of the combined effects of independent variables (pH, temperature, glucoamylase activity, kitchen waste loading, and hydrolysis time) as the most significant parameters for fermentable sugar production and degree of saccharification. A 100 mL of kitchen waste was hydrolyzed in 250 mL of shake flasks. Quadratic RSM predicted maximum fermentable sugar production of 62.79 g/L and degree of saccharification (59.90%) at the following optimal conditions: pH 5, temperature 60°C, glucoamylase activity of 85 U/mL, and utilized 60 g/L of kitchen waste as a substrate at 10 h hydrolysis time. The verification experiments successfully produced 62.71 ± 0.7 g/L of fermentable sugar with 54.93 ± 0.4% degree of saccharification within 10 h of incubation, indicating that the developed model was successfully used to predict fermentable sugar production at more than 90% accuracy. The sugars produced after hydrolysis of kitchen waste were mainly attributed to monosaccharide: glucose (80%) and fructose (20%). The fermentable sugars obtained were subsequently used as carbon source for bioethanol production by locally isolated yeasts: Saccharomyces cerevisiae, Candida parasilosis, and Lanchancea fermentati. The yeasts were successfully consumed as sugars hydrolysate, and produced the highest ethanol yield ranging from 0.45 to 0.5 g/g and productivity between 0.44 g L–1 h–1 and 0.47 g L–1 h–1 after 24-h incubation, which was equivalent to 82.06–98.19% of conversion based on theoretical yield.