Kunasundari Balakrishnan
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Kunasundari Balakrishnan
Official Name
Balakrishnan, Kunasundari
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Balakrishnan, K.
Kunasundari, B.
Kunasundari, Balakrishnan
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Scopus Author ID
37861493500
Researcher ID
DBC-0761-2022

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Structural and composition modification of Harum Manis mango (Mangifera indica) leaves via chemical pretreatment for bioethanol production

2023 , Mahadevan Tarrsini , Ng Qi Hwa , Yi Peng Teoh , Siew Hoong Shuit , Zhong Xian Ooi , Kunasundari Balakrishnan

Harum Manis mango leaves are considered lignocellulosic (LC) biomass that could contribute to the production of second generation (2G) bioethanol. However, pretreatment should be conducted to overcome the recalcitrance of LC biomass prior to bioethanol production. Hence, this study aims to elucidate the structural changes of the biomass of Harum Manis mango leaves after single-stage and two-stage chemical pretreatment. The Harum Manis mango leaves were treated with only acid, only alkaline, acid-alkaline, or alkaline-acid process. One per cent (v/v) sulphuric acid and 1% (w/v) sodium hydroxide were used as the acid and alkaline hydrolysing agent in the four approaches of pretreatment, respectively. Consequently, the pretreated biomass was enzymatically hydrolysed to produce reducing sugar followed by the conversion into bioethanol through yeast fermentation. Acid-alkaline pretreatment yielded the highest holocellulose composition of 95.26%, with the highest delignification effect of 86.97 ± 1.26%. Furthermore, Fourier transform infrared (FTIR) spectroscopy and X-ray powder diffraction (XRD) validated the acid-alkaline pretreated biomass to be the most feasible substrate for bioethanol production in this study. Finally, the maximum fermentable sugar content and bioethanol concentration of 415.02 ± 7.01 mg/g and 1.57 ± 0.06 mg/ml, respectively, were obtained.

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Functionalization of Multiwall Carbon Nanotubes (MWCNTS) using Phosphoric acid for immobilization of cellulase

2023 , Hasnol Azahari Natasha Yasmin , Thivagar Rao , Sandrasekaran Naresh , Siew Hoong Shuit , Kunasundari Balakrishnan

In this paper, functionalization of multiwall carbon nanotubes (MWCNTs) using phosphoric acid (H3 PO4 ) was attempted. Based on the One Factor at a Time (OFAT) analysis, 8 M of H3 PO4, 8 h of reflux time and 80 °C were identi-fied as an ideal condition for the acid oxidation process. Successful functionaliza-tion of MWCNTs using H3 PO4 was revealed from Fourier Transform Infrared Spectroscopy (FTIR) peaks and Scanning Electron Microscope (SEM) images. The resulting f-MWCNTs were immobilized with cellulase via adsorption. The optimum temperature for free cellulase was at 50 °C and for immobilized cel-lulase was at 60 °C. The optimum pH was at 5 for both free and immobilized cellulase. Higher thermal stability was achieved with immobilized cellulase in which 39% activity still was retained at 80 °C compared to free cellulase. Reus-ability study of immobilized cellulase depicted 28% of remaining activity after 5th cycle of analysis using model substrate (filter paper Whatman No. 1). These results suggest that H3 PO4 which is a mild acid is a promising substitution for functionalization of MWCNTs.

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Paddy straw saccharification using immobilized laccase on magnetized multiwall carbon nanotubes

2024-05 , Hasnol Azahari Natasha Yasmin , Kunasundari Balakrishnan , Siew Hoong Shuit , Mohamad Fahrurrazi Tompang

he effective recovery of the immobilized enzymes using magnetic carriers has led to growing interest in this technology. The objective of this research was to evaluate the efficiency of immobilized laccase on magnetized multiwall carbon nanotubes (m-MWCNTs) in terms of stability and reusability. Laccases were efficiently adsorbed onto magnetized multiwall carbon nanotubes (m-MWCNTs) synthesized using water. The concentration of 7 mg laccase/mL was found to be ideal for immobilization. The optimal activity of both free and immobilized laccases was observed at pH 5, while for the latter, the optimal temperature was shifted from 40 to 50 °C. Compared to the free laccase, the immobilized laccase exhibited a greater range of stability at more extreme temperatures. At the fourth cycle of reactions, the immobilized laccase exhibited more than 60% relative activity in terms of reusability. Based on the fourier-transform infrared spectroscopy (FTIR) peak at 2921 cm−1, saccharification of paddy straw using immobilized laccase verified lignin degradation. The easy recovery of the immobilized laccase on m-MWCNTs lends credence to its potential use in biomass hydrolysis.

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