Sains Malaysiana 50(2)(2021): 409-418

http://dx.doi.org/10.17576/jsm-2021-5002-12

Penghasilan Asid Laktik D daripada Hidrolisat Sabut Kelapa Tua dan Muda

(Production of D Lactic Acid from Hydrolysate Brown and Green Coconut Husk)

NUR NADHIRAH MUHAMAD NOR, TEO PUI LENG, NUR AKMAL SOLEHAH DIN & NURUL AQILAH MOHD ZAINI*

Jabatan Sains Makanan, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 46300 UKM Bangi, Selangor Darul Ehsan, Malaysia

Diserahkan: 4 Mac 2020/Diterima: 18 Ogos 2020

ABSTRAK

Penghasilan asid laktik D semakin mendapat perhatian kerana sifat polimernya, poli asid laktik D, yang termostabil. Kajian ini dijalankan untuk menghasilkan asid laktik D daripada sisa pertanian yang tidak bernilai tinggi seperti sabut kelapa tua (SKT) dan sabut kelapa muda (SKM) melalui teknologi fermentasi. Peringkat pertama kajian, SKT dan SKM dikenakan pra-rawatan beralkali menggunakan 5% larutan natrium hidroksida pada suhu 121 °C selama 15 minit untuk menyingkirkan komponen lignin dan hemiselulosa. Kemudian, dua kaedah hidrolisis dikaji, iaitu hidrolisis berenzim dengan menggunakan enzim Acellerase 1500 (1, 5 dan 10%, i/i) dan hidrolisis berasid dengan menggunakan asid sulfurik (1, 3 dan 5%, i/i). Keputusan menunjukkan hidrolisis berenzim dengan kepekatan 10% enzim Accellerase 1500 (11.09 mg/mL) lebih cekap menukarkan selulosa kepada gula penurun berbanding hidrolisis berasid (0.87 mg/mL) dalam hidrolisat SKT. Manakala, bagi hidrolisat SKM, 5% enzim Accellerase menghasilkan kepekatan gula penurun yang lebih tinggi berbanding hidrolisis berasid dengan 15.00 dan 1.02 mg/mL. Kadar penukaran gula penurun yang maksimum didapati daripada hidrolisis berenzim SKT dan SKM dengan 55% dan 60%. Pada peringkat kedua, hidrolisat yang mengandungi gula penurun yang tinggi digunakan sebagai sumber karbon untuk penghasilan asid laktik D oleh Lactobacillus coryniformis subsp. torquen melalui proses fermentasi (48 jam, 37 ºC, 150 rpm). Pada akhir proses fermentasi, sebanyak 4.93 g/L penghasilan asid laktik D direkodkan dalam kaldu hidrolisat SKT dan 3.98 g/L asid laktik D terhasil dalam kaldu hidrolisat SKM dengan pH kaldu fermentasi tidak dikawal. Kesimpulannya, selulosa dalam kedua-dua sampel SKT dan SKM boleh diuraikan kepada gula penurun melalui hidrolisis berenzim dan seterusnya berpotensi untuk digunakan sebagai substrat bagi menghasilkan asid laktik D melalui proses fermentasi.

Kata kunci: Asid laktik D; biojisim sabut kelapa; hidrolisis berenzim; hidrolisis berasid; proses fermentasi

ABSTRACT

Production of D lactic acid is gaining attention due to thermostable properties of its polymer, Poly-D-lactic acid. This study was conducted to produce D lactic acid from low-value agricultural waste such as brown coconut husk (SKT) and green coconut husk (SKM) through fermentation technology. In the first phase of the study, SKT and SKM were pre-treated with alkaline solution using 5% sodium hydroxide solution at 121 ° C for 15 min to remove lignin and hemicellulose components. Then, two hydrolysis methods were studied, namely enzymatic hydrolysis using Acellerase 1500 (1, 5 and 10%, v/v) and acidic hydrolysis using sulfuric acid (1, 3 and 5%, v/v). The results showed that 10% Accellerase 1500 (11.09 mg/mL) was more efficient in converting cellulose to reduced sugar than acidic hydrolysis (0.87 mg/mL) in SKT hydrolysis. Meanwhile, for SKM hydrolysis, 5% Accellerase enzyme yielded a higher sugar concentration than acidic hydrolysis with 15.00 and 1.02 mg/mL, respectively. The highest conversion rates of sugar were obtained from the hydrolysis of SKT and SKM by 55% and 60%, respectively. In the second stage of this research, hydrolysate of high reducing sugars was used as a carbon source for the production of D lactic acid by Lactobacillus coryniformis subsp. torquen through the fermentation (48 h, 37 ºC, 150 rpm). At the end of the fermentation process, 4.93 g/L of lactic acid production was recorded in SKT hydrolysate and 3.98 g/L lactic acid was produced in SKM hydrolysate, where the pH of the fermentation broth was not controlled. In conclusion, cellulose in both SKT and SKM samples can be hydrolysed into reducing sugars through enzymatic hydrolysis and subsequently shows potential to be used as a substrate for D lactic acid production through fermentation.

Keywords: Acidic hydrolysis; coconut husk biomass; D lactic acid; enzymatic hydrolysis; fermentation

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*Pengarang untuk surat-menyurat; email: nurulaqilah@ukm.edu.my