Mutagenic and antimutagenic activities of lactic acid bacteria (LAB) Lactobacillus plantarum isolated from the local fermented durian (tempoyak) was determined by Ames test (Salmonella/microsome mutagenicity assay). Our study also involved pre-incubation assay against Salmonella typhimurium TA 98 and TA 100 bacterial strain in the presence and absence of metabolic activator S9 system. It was found that the L. plantarum showed no mutagenic activity on both S. typhimurium strain TA 98 and TA 100 in the presence and absence of metabolic activator. Significant antimutagenic activity (p < 0.05) was observed in both cell-free supernatant and bacterial cell suspension of L. plantarum as compared to the mutagenicity induced by 2-Aminoanthracene in the presence of metabolic activator. Meanwhile, in the absence of metabolic activator, only the bacterial cells of L. plantarum showed antimutagenicity acitivity against Sodium Azide and 2-Nitrofluorene. In conclusion, L. plantarum could play a vital role as chemopreventive agent by binding to mutagens and suppressing mutagenesis. Thus, L. plantarum could be consider as a good candidate for functional food development as a supplement product to prevent development of colon cancer.
Possible application of a locally isolated environmental isolate, Acinetobacter haemolyticus to remediate Cr(VI) contamination in water system was demonstrated. Cr(VI) reduction by A. haemolyticus seems to favour the lower concentrations (10-30 mg/L). However, incomplete Cr(VI) reduction occurred at 70-100 mg/L Cr(VI). Initial specific reduction rate increased with Cr(VI) concentrations. Cr(VI) reduction was not affected by 1 or 10 mM sodium azide (metabolic inhibitor), 10 mM of PO(4)3-, SO4(2-), SO(3)2-, NO3- or 30 mg/L of Pb(II), Zn(II), Cd(II) ions. However, heat treatment caused significant dropped in Cr(VI) reduction to less than 20% only. A. haemolyticus cells loses its shape and size after exposure to 10 and 50 mg Cr(VI)/L as revealed from TEM examination. The presence of electron-dense particles in the cytoplasmic region of the bacteria suggested deposition of chromium in the cells.
5'-Phosphodiesterase (5'-PDE) is an enzyme that hydrolyses RNA to form 5'-inosine monophosphate (5'-IMP) and 5'-guanosine monophosphate (5'-GMP), which function as flavour enhancers. Selection of the best producer of 5'-PDE was made by determining the activity of the enzyme in six seeds that have been germinated, namely mung bean (Vigna radiate), soybean (Glycine max), adzuki/red bean (Vigna angularis L.), chick pea (Cicer arietinum), black eye pea (Vigna unguiculata) and petai (Parkia speciosa). Seeds that were not germinated acted as the control. In order to ensure there is no contamination from potential 5'-PDE-producing microorganisms during germination, microbial growth was reduced by using different surface sterilizing treatments where the seeds were soaked in 100 mL solution containing different concentrations of sodium hypochlorite (with or without 0.05% sodium azide) for 5 minutes before rinsing it five times with sterilized distilled water (total 500 mL). The seeds were observed every day for 3 days and the best surface sterilizing treatment was selected based on absence of mold growth and the effects on hypocotyl length. Sodium hypochlorite at 0.3% (v/v) concentration was able to inhibit mold growth in adzuki bean, soybean and chickpea. On the other hand, only 0.1% (v/v) sodium hypochlorite was needed to inhibit mold growth in black eye pea and petai, while mung bean required 0.05% (v/v) sodium hypochlorite to inhibit mold growth. Under these conditions, the growth of hypocotyl (hypocotyls length) was only slightly affected compared to the control. 5'-PDE was extracted from seeds that have been germinated for 24 hours and their control (ungerminated seeds) by homogenization in a blender with 400 mL of 50 mM acetate buffer, pH 4.5. After that, the homogenates were stirred for 30 min and the centrifuged at 9000 rpm for 15 min at 10°C. 5'-PDE activity was determined using thymidine 5'-monophosphate p-nitrophenyl ester as substrate at pH 7.0 and 55°C. The formation of nucleotide monophosphates, the products of reaction, was determined at 405 nm. As a strong presence of phosphomonoesterase (PME) will reduce the yield of nucleotide monophosphates as the enzyme hydrolyzes these products into nucleosides and orthophosphate, PME activity was also determined using p-nitrophenyl phosphate as the substrate at 60°C and pH 5.0. Thus, the seed with the highest 5'-PDE activity and a low PME activity can be selected. Germinated adzuki bean was found to have the highest 5'-PDE activity (0.59 µmol p-nitrophenol/min/mg protein) among the germinated seeds. A time-course study indicated that the level of 5'-PDE in adzuki bean increased with time of germination until 15 hours (0.69 µmol p-nitrophenol/min/mg protein), after which the acitivity decreased until it reached the basal level (0.44 µmol p-nitrophenol/min/mg protein) at 72 hours. On the other hand, PME in the bean was the highest at 9 h germination (0.98 µmol p-nitrophenol/min/mg protein). In general, controls have very low basal level of 5'-PDE activity (0.18- 0.42 µmol p-nitrophenol/min/mg protein).