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Biochemical properties of xylose reductase prepared from adapted strain of Candida tropicalis

Rafiqul IS, Sakinah AM

Appl Biochem Biotechnol, 2015 Jan;175(1):387-99.
PMID: 25300602 DOI: 10.1007/s12010-014-1269-4

Xylose reductase (XR) is an intracellular enzyme, which catalyzes xylose to xylitol conversion in the microbes. It has potential biotechnological applications in the manufacture of various commercially important specialty bioproducts including xylitol. This study aimed to prepare XR from adapted strain of Candida tropicalis and to characterize it. The XR was isolated from adapted C. tropicalis, cultivated on Meranti wood sawdust hemicellulosic hydrolysate (MWSHH)-based medium, via ultrasonication, and was characterized based on enzyme activity, stability, and kinetic parameters. It was specific to NADPH with an activity of 11.16 U/mL. The enzyme was stable at pH 5-7 and temperature of 25-40 °C for 24 h and retained above 95 % of its original activity after 4 months of storage at -80 °C. The K m of XR for xylose and NADPH were 81.78 mM and 7.29 μM while the V max for them were 178.57 and 12.5 μM/min, respectively. The high V max and low K m values of XR for xylose reflect a highly productive reaction among XR and xylose. MWSHH can be a promising xylose source for XR preparation from yeast.
Production of High Commercial Value Xylooligosaccharides from Meranti Wood Sawdust Using Immobilised Xylanase

Sukri SSM, Mimi Sakinah AM

Appl Biochem Biotechnol, 2018 Jan;184(1):278-290.
PMID: 28676961 DOI: 10.1007/s12010-017-2542-0

The present study explores the utilisation of a new raw material from lignocellulose biomass, Meranti wood sawdust (MWS) for high commercial value xylooligosaccharides (XOS) production using immobilised xylanase. The xylanase was immobilised by a combination of entrapment and covalent binding techniques. The hemicellulosic xylan from MWS was extracted using a standard chlorite delignification method. The production of total and derivatives of XOS from the degradation of the hemicellulosic xylan of MWS were compared to the production from the commercial xylan from Beechwood. The utilisation of the extracted xylan from MWS yielded 0.36 mg/mL of total XOS after 60 h of hydrolysis. During the hydrolysis reaction, the immobilised xylanase released a lower degree of polymerisation (DP) of XOS, mainly X2 and X3, which were the major products of xylan degradation by xylanase enzymes. The production of XOS with a lower DP from MWS demonstrated the biotechnological potential of the MWS in the future. The XOS production retained about 70% of its initial XOS production during the second cycle. This is also the first report on the utilisation of MWS wastes in enzymatic hydrolysis using immobilised xylanase for XOS production.
Terbutaline for acute tocolysis prior to emergency caesarean delivery for suspected foetal compromise

Zahar AZ, Azny MY, Sakinah A, Gayathiri M

Med J Malaysia, 2023 Jan;78(1):93-97.
PMID: 36715198

INTRODUCTION: Terbutaline has been used as a foetal resuscitation measure to improve the intrapartum foetal heart rate abnormalities and neonatal outcome for suspected foetal compromise. Unfortunately, till date, the available data are limited to draw any recommendation.
MATERIAL AND METHODS: This was a double-blind, placebocontrolled trial conducted among women planned for emergent caesarean delivery for suspected foetal compromise where 100 were randomised to receive subcutaneous terbutaline or placebo. The primary outcomes were the neonatal acid-base status, while the 5- minute Apgar score, admission to the intensive care unit and the maternal outcomes were recorded as secondary outcomes.
RESULTS: Data from a total of 96 women were analysed and showed a lower incidence of neonatal acidemia (4.4% vs 10.4%) and fewer neonates born with umbilical artery pH of less than 7.20 (12.5% vs 27.1%) and 7.10 (4.2% vs 6.2%) after terbutaline injection. However, the difference in the incidence of neonatal acidaemia, mean cord pH and base excess, Apgar score or admission to the intensive care unit did not differ significantly. No difference was seen in the maternal mean arterial pressure, estimated blood loss or haematocrit after the surgery between the study groups. The only significant maternal effect was tachycardia which was more common after terbutaline injection (54.2% vs 25.0 %, p=0.003).
CONCLUSION: The study shows that acute tocolysis with subcutaneous terbutaline prior to caesarean delivery has the potential to improve the neonatal outcome in suspected intrauterine foetal compromise and should be further investigated.
Production of xylose from Meranti wood sawdust by dilute acid hydrolysis

Rafiqul IS, Sakinah AM, Karim MR

Appl Biochem Biotechnol, 2014 Sep;174(2):542-55.
PMID: 25082763 DOI: 10.1007/s12010-014-1059-z

Xylitol production by bioconversion of xylose can be economically interesting if the raw material can be recovered from a cheap lignocellulosic biomass (LCB). Meranti wood sawdust (MWS) is a renewable and low-cost LCB that can be used as a promising and economic source of xylose, a starting raw material for the manufacture of several specialty chemicals, especially xylitol. This study aimed to optimize the hydrolysis process of MWS and to determine the influence of temperature, H2SO4 concentration, and residence time on xylose release and on by-product formation (glucose, arabinose, acetic acid, furfural, hydroxymethylfurfural (HMF), and lignin degradation products (LDPs)). Batch hydrolysis was conducted under various operating conditions, and response surface methodology was adopted to achieve the highest xylose yield. Xylose production was highly affected by temperature, acid concentration, and residence time. The optimum temperature, acid concentration, and time were determined to be 124 °C, 3.26 %, and 80 min, respectively. Under these optimum conditions, xylose yield and selectivity were attained at 90.6 % and 4.05 g/g, respectively.
Inhibition by toxic compounds in the hemicellulosic hydrolysates on the activity of xylose reductase from Candida tropicalis

Rafiqul IS, Sakinah AM, Zularisam AW

Biotechnol Lett, 2015 Jan;37(1):191-6.
PMID: 25214231 DOI: 10.1007/s10529-014-1672-5

Xylose reductase (XR) is an oxidoreductase having potential applications in the production of various specialty products, mainly xylitol. It is important to screen for compounds that can decrease XR activity and consequently can decrease xylitol production. We have identified the byproducts in the hemicellulosic hydrolysate that inhibit XR from Candida tropicalis and measured their effects. XR inhibitory activities of byproducts, glucose, acetic acid, arabinose, lignin-degradation products (LDPs), furfural and hydroxymethylfurfural (HMF), were evaluated by measuring the MIC and IC50 values. XR activity was 11.2 U/ml. Acetic acid, LDPs, furfural and HMF significantly inhibited XR with IC50 values of 11, 6.4, 2.3 and 0.4 g/l, respectively. This is the first report on the inhibitory activities of several byproducts for XR.
Enzymatic Production of Bioxylitol from Sawdust Hydrolysate: Screening of Process Parameters

Rafiqul IS, Sakinah AM, Zularisam AW

Appl Biochem Biotechnol, 2015 Jun;176(4):1071-83.
PMID: 25904039 DOI: 10.1007/s12010-015-1630-2

Xylose-rich sawdust hydrolysate can be an economic substrate for the enzymatic production of xylitol, a specialty product. It is important to identify the process factors influencing xylitol production. This research aimed to screen the parameters significantly affecting bioxylitol synthesis from wood sawdust by xylose reductase (XR). Enzymatic bioxylitol production was conducted to estimate the effect of different variables reaction time (2-18 h), temperature (20-70 °C), pH (4.0-9.0), NADPH (1.17-5.32 g/L), and enzyme concentration (2-6 %) on the yield of xylitol. Fractional factorial design was followed to identify the key process factors. The screening design identified that time, temperature, and pH are the most significant factors influencing bioxylitol production among the variables with the values of 12 h, 35 °C, and 7.0, respectively. These conditions led to a xylitol yield of 71 % (w/w). This is the first report on the statistical screening of process variables influencing enzyme-based bioxylitol production from lignocellulosic biomass.
Hylocereus polyrhizus peel's high-methoxyl pectin: A potential source of hypolipidemic agent

Zaid RM, Mishra P, Wahid ZA, Sakinah AMM

Int J Biol Macromol, 2019 Aug 01;134:361-367.
PMID: 31059740 DOI: 10.1016/j.ijbiomac.2019.03.143

In the present study, high-methoxyl pectin (HMP) was extracted from Hylocereus polyrhizus peel's using physico-chemical process. In addition, the hypolipidemic activity of HMP was investigated at different concentration and time corresponding to its adsorption ability. FTIR and contact angle analysis were used to determine the sorbent characterization. A high degree of esterification (63.8%) and the contact angle (95.5°) confirmed hydrophobic nature and resulting bad wetting of the HMP extract, respectively. The methoxyl content in the pectin acted as an affinity-precursor of the pectin towards cholesterol due to its increased hydrophobicity. The maximum equilibrium uptake capacity of cholesterol of 370.5mg/g (0.96mmol/g) was observed by HMP. The experimental data showed good fitting for Freundlich isotherm equation and followed pseudo-first-order kinetic model with a correlation coefficient (R2) of 0.89-0.97 due to physisorption mechanism. Intra-particle model confirmed that the cholesterol sorption rate by HMP was significantly influenced by external mass transfer (surface diffusion) and intra-particle diffusion (diffusion control). It was also revealed that the HMP extracted from Hylocereus polyrhizus peels possess a high affinity towards cholesterol, making it an ideal hypolipidemic agent.
Fulltext Glycerol waste to value added products and its potential applications

Chilakamarry CR, Sakinah AMM, Zularisam AW, Pandey A

Syst Microbiol Biomanuf, 2021;1(4):378-396.
PMID: 38624889 DOI: 10.1007/s43393-021-00036-w

The rapid industrial and economic development runs on fossil fuel and other energy sources. Limited oil reserves, environmental issues, and high transportation costs lead towards carbon unbiased renewable and sustainable fuel. Compared to other carbon-based fuels, biodiesel is attracted worldwide as a biofuel for the reduction of global dependence on fossil fuels and the greenhouse effect. During biodiesel production, approximately 10% of glycerol is formed in the transesterification process in a biodiesel plant. The ditching of crude glycerol is important as it contains salt, free fatty acids, and methanol that cause contamination of soil and creates environmental challenges for researchers. However, the excessive cost of crude glycerol refining and market capacity encourage the biodiesel industries for developing a new idea for utilising and produced extra sources of income and treat biodiesel waste. This review focuses on the significance of crude glycerol in the value-added utilisation and conversion to bioethanol by a fermentation process and describes the opportunities of glycerol in various applications.
High methoxyl pectin extracts from Hylocereus polyrhizus's peels: Extraction kinetics and thermodynamic studies

Zaid RM, Mishra P, Tabassum S, Wahid ZA, Sakinah AMM

Int J Biol Macromol, 2019 Dec 01;141:1147-1157.
PMID: 31494156 DOI: 10.1016/j.ijbiomac.2019.09.017

The effect of physicochemical treatment on pectin yield, degree of esterification, along with the kinetics and thermodynamics characteristics was investigated in the present study. Several extraction parameters were observed to have impacted the yield and degree of esterification significantly, and the best extraction condition was as follows: agitation rate of 250 rpm, temperature of 70 °C, extraction time of 120 min, pH 2, and liquid to solid ratio of 10 v/w which has resulted in 28.20% of pectin yield, with DE (degree of esterification) of 57.00%. A theoretical model which describes the extractability, dissolution and degradation rate of pectin to predict the maximal yield at the maximal time was established to study the extraction kinetics of pectin from HPP. The kinetic analysis from Panchev's model shows the extraction rate was found highest at LSR 10 with ymax 30.85%. The calculated activation energy for pectin dissolution and degradation was found to be 4.532 kJ/mol and 28.054 kJ/mol, respectively. The thermodynamic study has suggested that the process was endothermic, spontaneous and reversible. These results suggest that the physical and chemical treatment applied could be an efficient technique for the extraction of pectin from Hylocereus polyrhizus peels.
Advances in solid-state fermentation for bioconversion of agricultural wastes to value-added products: Opportunities and challenges

Chilakamarry CR, Mimi Sakinah AM, Zularisam AW, Sirohi R, Khilji IA, Ahmad N, et al.

Bioresour Technol, 2022 Jan;343:126065.
PMID: 34624472 DOI: 10.1016/j.biortech.2021.126065

The increase in solid waste has become a common problem and causes environmental pollution worldwide. A green approach to valorise solid waste for sustainable development is required. Agricultural residues are considered suitable for conversion into profitable products through solid-state fermentation (SSF). Agricultural wastes have high organic content that is used as potential substrates to produce value-added products through SSF. The importance of process variables used in solid-phase fermentation is described. The applications of SSF developed products in the food industry as flavouring agents, acidifiers, preservatives and flavour enhancers. SSF produces secondary metabolites and essential enzymes. Wastes from agricultural residues are used as bioremediation agents, biofuels and biocontrol agents through microbial processing. In this review paper, the value addition of agricultural wastes by SSF through green processing is discussed with the current knowledge on the scenarios, sustainability opportunities and future directions of a circular economy for solid waste utilisation.