Mimi Sakinah

Targeting N-acyl-homoserine-lactones to mitigate membrane biofouling based on quorum sensing using a biofouling reducer

Exploring novel biological anti-quorum sensing (QS) agents to control membrane biofouling is of great worth in order to allow sustainable performance of membrane bioreactors (MBRs) for wastewater treatment. In recent studies, QS inhibitors have provided evidence of alternative route to control membrane biofouling. This study investigated the role of Piper betle extract (PBE) as an anti-QS agent to mitigate membrane biofouling. Results demonstrated the occurrence of the N-acyl-homoserine-lactone (AHL) autoinducers (AIs), correlate QS activity and membrane biofouling mitigation. The AIs production in bioreactor was confirmed using an indicator strain Agrobacterium tumefaciens (NTL4) harboring plasmid pZLR4. Moreover, three different AHLs were found in biocake using thin layer chromatographic analysis. An increase in extracellular polymeric substances (EPS) and transmembrane pressure (TMP) was observed with AHL activity of the biocake during continuous MBR operation, which shows that membrane biofouling was in close relationship with QS activity. PBE was verified to mitigate membrane biofouling via inhibiting AIs production. SEM analysis further confirmed the effect of PBE on EPS and biofilm formation. These results exhibited that PBE could be a novel agent to target AIs for mitigation of membrane biofouling. Further work can be carried out to purify the active compound of Piper betle extract to target the QS to mitigate membrane biofouling.

Biofouling mitigation using Piper betle extract in ultrafiltration MBR

AbstractThe control of membrane biofouling in the presence of Piper betle extract (PBE) as a biofouling reducer (BFR) has been investigated. Response surface methodology (RSM) has been employed to mitigate extracellular polymeric substances (EPS), transmembrane pressure (TMP) rise-up control, and dye removal in membrane bioreactor. Factors investigated were: BFR dosage, air flow rate, and hydraulic retention time (HRT). Optimum conditions found to be BFR of 0.23 mg/mg mixed liquor suspended solids, HRT of 30.16 h, and air flow rate of 0.60 l/min, with predicted values as 28.28 mg/l of EPS, 24.16 kPa of TMP, and 95.65% dye removal, respectively. Validatory tests were carried out under the optimum conditions, which were closely agreed with the predicted values. These results depicted that RSM was one of the suitable methods to optimize the operating conditions to mitigate fouling in the presence of a BFR. PBE was verified to mitigate membrane biofouling via inhibiting autoinducers production. Furthermore, i...

Lead induced oxidative stress and alteration in the activities of antioxidative enzymes in rice shoots

Physiological responses of Oryza sativa L. to lead excess (10 and 50 μM) were studied in a hydroponic system after 48- and 96-h exposure. Accumulation of Pb in stressed rice shoots was concomitant with an increased metal concentration in the growth media and duration of exposure. The Pb stress resulted in an enhanced lipid peroxidation accompanied by altered activities of antioxidants. A substantial increase in α-tocopherol content of the Pb stressed rice shoots was observed suggesting its important role as an antioxidant. Among the antioxidant enzymes studied, activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) increased in the Pb-treated rice shoots, whereas that of catalase (CAT) declined. Activity of an important ascorbate-glutathione cycle enzyme, glutathione reductase (GR), also increased significantly in the Pb-treated shoots. The results suggest that Pb toxicity resulted in induction of oxidative stress in rice shoots, and α-tocopherol accumulation and upregulation of SOD, APX, and GR activities play an effective role in acclimatization to Pb stress.