Mohamed Ismail Abdul Karim

Direct fermentation of gelatinized sago starch to acetone-butanol-ethanol by Clostridium acetobutylicum

Direct fermentation of gelatinized sago starch into solvent (acetone–butanol–ethanol) by Clostridium acetobutylicum P262 was studied using a 250 ml Schott bottle anaerobic fermentation system. Total solvent production from fermentation using 30 g sago starch/l (11.03g/l) was comparable to fermentation using corn starch and about 2-fold higher than fermentation using potato or tapioca starch. At the range of sago starch concentration investigated (10–80 g/l), the highest total solvent production (18.82 g/l) was obtained at 50 g/l. The use of a mixture of organic and inorganic nitrogen source (yeast extract + NH4NO3) enhanced growth of C. acetobutylicum, starch hydrolysis and solvent production (24.47 g/l) compared to the use of yeast extract alone. This gave the yield based on sugar consumed of 0.45 g/g. Result from this study also showed that the individual concentrations of nitrogen and carbon influenced solvent production to a greater extent than did carbon to nitrogen (C/N) ratio.

Detection of Escherichia coli O157:H7 by multiplex PCR and their characterization by plasmid profiling, antimicrobial resistance, RAPD and PFGE analyses

Twenty-five and three strains of Escherichia coli O157:H7 were identified from 25 tenderloin beef and three chicken meat burger samples, respectively. The bacteria were recovered using the immunomagnetic separation procedure followed by selective plating on sorbitol MacConkey agar and were identified as E. coli serotype O157:H7 with three primer pairs that amplified fragments of the SLT-I, SLT-II and H7 genes in PCR assays. Susceptibility testing to 14 antibiotics showed that all were resistant to two or more antibiotics tested. Although all 28 strains contained plasmid, there was very little variation in the plasmid sizes observed. The most common plasmid of 60 MDa was detected in all strains. We used DNA fingerprinting by randomly amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE) to compare the 28 E. coli O157:H7 strains. At a similarity level of 90%, the results of PFGE after restriction with XbaI separated the E. coli O157:H7 strains into 28 single isolates, whereas RAPD using a single 10-mer oligonucleotides separated the E. coli O157:H7 strains into two clusters and 22 single isolates. These typing methods should aid in the epidemiological clarification of the E. coli O157:H7 in the study area.

Enzyme production and profile by Aspergillus niger during solid substrate fermentation using palm kernel cake as substrate

The oil palm sector is one of the major plantation industries in Malaysia. Palm kernel cake is a byproduct of extracted palm kernel oil. Mostly palm kernel cake is wasted or is mixed with other nutrients and used as animal feed, especially for ruminant animals. Recently, palm kernel cake has been identified as an important ingredient for the formulation of animal feed, and it is also exported especially to Europe, South Korea, and Japan. It can barely be consumed by nonruminant (monogastric) animals owing to the high percentages of hemicellulose and cellulose contents. Palm kernel cake must undergo suitable pretreatment in order to decrease the percentage of hemicellulose and cellulose. One of the methods employed in this study is fermentation with microorganisms, particularly fungi, to partially degrade the hemicellulose and cellulose content. This work focused on the production of enzymes by Aspergillus niger and profiling using palm kernel cake as carbon source.

The kinetics and mechanism of lead (II) biosorption by powderized Rhizopus oligosporus

The kinetics and mechanism of lead biosorption by powderized Rhizopus oligosporus were studied using shake flask experiment. The optimum biomass concentration and initial solution pH for lead sorption at initial lead concentrations ranging from 50–200 mg/l was obtained at 0.5 g/l and pH5, respectively. In term of the ratio of initial lead concentration to biomass concentration ratio, the highest lead adsorption was obtained at 750 mg/g which gave the maximum lead uptake capacity of 126 mg/g. The experimental data of lead sorption by R.oligosporus fitted well to the Langmuir sorption isotherm model, indicating that the sorption was similar to that for an ion-exchange resin. This means that the sorption is a single layer metal adsorption that occurred as a molecular surface coverage. This assumption was confirmed by the examination of lead sorption using transmission electron microscope and energy dispersive X-ray analysis, which showed that during sorption most of the lead was adsorbed on the surface of cell.

The mechanism of cadmium removal from aqueous solution by nonmetabolizing free and immobilized live biomass of Rhizopus oligosporus

A preliminary study on the removal of cadmium by nonmetabolizing live biomass of Rhizopus oligosporus from aqueous solution is presented. The equilibrium of the process was in all cases well described by the Langmuir sorption isotherm, suggesting that the process was a chemical, equilibrated and saturable mechanism which reflected the predominantly site-specific mechanism on the cell surface. A curve of Scatchard transformation plots reflected the covalent nature of Cd2+ adsorption by the cells. The maximum cadmium uptake capacities were 34.25 mg/g for immobilized cells and 17.09 mg/g for free cells. Some factorial experiments in shake flasks were performed in order to investigate the effect of different initial cadmium concentrations and biomass concentrations on the equilibrium. Experimental results showed a reverse trend of the influence of the immobilized and free biomass concentration on the cadmium specific uptake capacity. The immobilized cells had a higher specific cadmium uptake capacity with increasing biomass concentrations compared to free cells. In a bioreactor, the cadmium uptake capacity of immobilized cells (qmax = 30.1–37.5 mg/g) was similar to that observed in shake flask experiments (qmax = 34.25 mg/g) whereas with free cells the bioreactor qmax of 4.8–13.0 mg/g; was much lower than in shake flasks (qmax = 17.09 mg/g), suggesting that cadmium biosorption by immobilized cells of R. oligosporus might be further improved in bigger reactors. EDAX and transmission electron microscopic experiments on the fungal biomass indicated that the presence of Cd2+ sequestrated to the cell wall was due to bioadsorption.

Anaerobic fermentation of gelatinized sago starch-derived sugars to acetone-1-butanol-ethanol solvent by Clostridium acetobutylicum.

A study of the kinetics and performance of solvent-yielding batch fermentation of individual sugars and their mixture derived from enzymic hydrolysis of sago starch byClostridium acetobutylicum showed that the use of 30 g/L gelatinized sago starch as the sole carbon source produced 11.2 g/L total solvent,i.e. 1.5–2 times more than with pure maltose or glucose used as carbon sources. Enzymic pretreatment of gelatinized sago starch yielding maltose and glucose hydrolyzates prior to the fermentation did not improve solvent production as compared to direct fermentation of gelatinized sago starch. The solvent yield of direct gelatinized sago starch fermentation depended on the activity and stability of amylolytic enzymes produced during the fermentation. The pH optima for α-amylase and glucoamylase were found to be at 5.3 and 4.0–4.4, respectively. α-Amylase showed a broad pH stability profile, retaining more than 80% of its maximum activity at pH 3.0–8.0 after a 1-d incubation at 37°C. SinceC. acetobutylicum α-amylase has a high activity and stability at low pH, this strain can potentially be employed in a one-step direct solvent-yielding fermentation of sago starch. However, theC. acetobutylicum glucoamylase was only stable at pH 4–5, maintaining more than 90% of its maximum activity after a 1-d incubation at 37°C.

Aeration and yeast extract requirements for kojic acid production by Aspergillus flavus link

Growth and kojic acid production by Aspergillus flavus Link 44-1 were studied at different levels of dissolved oxygen tension (DOT) using a 2-l stirred tank fermenter. In all experiments, agitation was fixed at 600 rpm and DOT was controlled at different levels by varying airflow rates. Single-phase DOT control at three different levels (30, 50, and 80% saturation) did not enhance kojic acid production when compared to fermentation without DOT control (13.5 g l-l). The production of kojic acid in a fermentation with single-phase DOT control at 80% was comparable to that of a fermentation without DOT control. Decreased DOT levels below 80% reduced the production of kojic acid significantly although the biomass increased. When DOT was controlled at a very high level (80%) during active growth and then decreased to a low level (30%) during the production phase (i.e., two-phase DOT control), the production of kojic acid (28.9 g l-l) was increased by about two times compared to a fermentation without DOT control; however, when yeast extract was added continuously in a fermentation with two-phase DOT control, active growth occurred during the production phase and the maximum accumulation of kojic acid was reduced significantly. High DOT during on active growth phase and no addition of yeast extract during the production phase were required to enhance kojic acid biosynthesis. The most effective control strategy for kojic acid production, therefore, was to control DOT at very high levels during active growth and not add a nitrogen source during the production phase while using low levels of DOT.

Biological treatment of palm oil mill effluent using Trichoderma viride

Abstract Research was undertaken to investigate the treatment of palm oil mill effluent (POME) using the fungus Trichoderma viride to reduce its wastewater strength, and to recover the microbial mass. More than 95% reductin in Chemical Oxygen Demand (COD) of the POME was achieved after 10–14 days of fermentation. The fungal biomass produced from the POME was 1·37–1·42 g/litre (dry weight) of mycelium with a crude protein content of 37·6–40·7%.

The use of coagulating and polymeric flocculating agents in the treatment of palm oil mill effluent (POME)

Abstract The reduction of pollution strength in palm oil mill effluent (POME) using five inorganic salts and nine polymers was investigated. Treatment of POME with 80–100 mg litre −1 of Magnafloc LT22 polymer aided in coagulation and flocculation of Total Suspended Solids, producing 96%, 63%, 53% and 93–94% reduction in the turbidity, chemical oxygen demand (COD), Total Solids (TS) and Total Suspended Solids (TSS) respectively, of the effluent. Treatment with 200 to 300 mg litre −1 FeCl 3 + 70 to 100 mg litre −1 Magnafloc LT22 polymer reduced COD, TS and TSS by 47 to 53%, 43 to 49% and 92 to 94%, respectively. The TSS of POME can be substantially reduced by treating with coagulating and flocculating agents before discharging into other treatment systems.

Importance of carbon source feeding and pH control strategies for maximum kojic acid production from sago starch by Aspergillus flavus

Abstract To maximize kojic acid production by Aspergillus flavus Link 44-1 using gelatinized sago starch as a carbon source, the performance of different fermentation modes (batch and fed-batch with different feeding modes) was investigated in an 8- l stirred tank fermentor. The addition of a large volume of concentrated sago starch (140 g/ l ) 2 d after the start with an initial starch concentration of 60 g/ l produced the maximum concentration of kojic acid (16.43 g/ l ), which was about 4 times higher than that for batch fermentation of 100 g/ l sago starch. Further improvement of kojic acid production was obtained by adding small amounts of concentrated starch (140 g/ l ) intermittently at 2-d intervals to the culture. Using this technique of fermentation, the dissolved oxygen tension (DOT) can be controlled at high levels (40–50% saturation) during the active growth phase, which is required for the enhanced secretion of α-amylase used for saccharification of starch and also for the production of mycelia with higher ability in synthesizing kojic acid. Maintaining the culture pH at 3 throughout the intermittent fed-batch fermentation reduced kojic acid production (7.26 g/ l ) significantly. Very little kojic acid (0.93 g/ l ) was produced when the pH was kept at 4 during the growth phase and then lowered to 3 during the production phase. A high level of kojic acid production (31.00 g/ l ) was achieved in fermentation where the pH was not controlled throughout the cultivation or not controlled during the growth phase but kept at 3 during the production phase. This result indicates that the pH control strategy is important; with the variation in culture pH during the growth phase being most significant and critical to kojic acid production.