Optimization and Scale-Up of Solid-State Bioconversion for Microbial Coagulant Production toward Sustainable Water Treatment

Abstract

Microbial coagulants are emerging as an eco-friendly alternative to chemical coagulants owing to their non-toxicity, biodegradability, and sustainability. However, their use is limited by high production costs linked to expensive nutrient media and scalability issues. To address these challenges, this study developed a cost-effective microbial coagulant based on a fungus using cocopeat as a substrate. Growth conditions (malt extract, glucose, and pH) were optimized using the Face-Centered Central Composite Design (FCCCD) under Response Surface Methodology (RSM) to maximize coagulant yield. The performance in water treatment was evaluated using jar tests, and large-scale production techniques were investigated using a tray bioreactor and an agitated drum bioreactor (ADB). The fungal strain used in this study was identified as Phanerochaete concrescens, which demonstrated high turbidity-reducing efficiency, achieving a maximum flocculating activity of 93.06% in a standard jar test. These results were obtained under statistically optimized growth conditions, specifically 5 days of incubation at 25°C, 70% moisture content, 3% malt extract, 2.5% glucose, and pH 7, confirming model predictions. Phanerochaete concrescens was successfully scaled using a tray fermenter, achieving a flocculation rate of 92% after 5 days of incubation at 70% moisture, pH 7, and a 3 cm substrate thickness. However, in a 30 L agitated bioreactor drum, flocculating activity was recorded at 29% due to insufficient fungal growth at the tested agitation rate. This study confirms the feasibility of a cost-effective microbial coagulant that can be scaled appropriately, offering a sustainable and biodegradable alternative to chemical coagulants.

ABSTRAK: Koagulan mikrob muncul sebagai alternatif mesra alam pada koagulan kimia kerana sifatnya yang tidak toksik, terbiodegradasi, dan mampan. Walau bagaimanapun, penggunaannya terhad kerana kos pengeluaran tinggi disebabkan oleh media nutrien yang mahal dan isu kebolehskalaan. Bagi menangani cabaran ini, kajian ini membangunkan koagulan mikrob kos efektif berdasarkan kulapuk kokopit sebagai substrat. Keadaan pertumbuhan (ekstrak malt, glukosa, dan pH) dioptimumkan menggunakan Reka Bentuk Komposit Berpusat Muka (FCCCD) di bawah Kaedah Gerak Balas Permukaan (RSM) bagi memaksimum hasil koagulan. Prestasi dalam rawatan air dinilai menggunakan ujian balang, dan teknik pengeluaran skala besar dikaji menggunakan bioreaktor dulang dan bioreaktor dram bergoncang (ADB). Strain kulat yang digunakan dalam kajian ini dikenal pasti sebagai Phanerochaete concrescens, menunjukkan kecekapan tinggi dalam mengurangkan kekeruhan, mencapai aktiviti pengflokulan maksimum 93.06% melalui ujian piawai balang. Keputusan ini diperoleh di bawah keadaan pertumbuhan yang optimum secara statistik, iaitu 5 hari pengeraman pada suhu 25°C, kandungan lembapan 70%, ekstrak malt 3%, glukosa 2.5%, dan pH 7, mengesahkan model ramalan. Phanerochaete concrescens berjaya diskala menggunakan penapai dulang, dengan kadar pengflokulan 92% dicapai selepas 5 hari pengeraman di bawah lembapan 70%, pH 7, dan ketebalan substrat 3 cm. Walau bagaimanapun, dalam dram bioreaktor bergoncang 30 L, aktiviti pengflokulan direkodkan pada 29% disebabkan oleh pertumbuhan kulat yang tidak mencukupi pada kadar goncangan yang diuji. Kajian ini mengesahkan kebolehlaksanaan koagulan mikrob kos efektif pada skala wajar, menawarkan alternatif mampan dan terbiodegradasi pada koagulan kimia.