Kanokphorn Sangkharak

The production of polyhydroxyalkanoate by Bacillus licheniformis using sequential mutagenesis and optimization

The purpose of this study was to enhance the production of polyhydroxyalkanoate (PHA) by sequential mutation of Bacillus licheniformis PHAs-007, using UV and N-methyl-N′-nitro-N-nitrosoguanidine (NTG). In addition, the effect of nutrient additions and environmental conditions were optimized to increase the production of PHA. Bacillus licheniformis PHAs-007 produced high amounts of PHA (64.09 ∼ 68.80% of DCW) under both synthetic and renewable substrates. After mutagenesis treatment, mutant M2-12 was selected from 380 strains, based on its high biomass and PHA concentration. The mutant M2-12 gave the highest value of specific growth rate (0.09/h), biomass (22.24 g/L) and PHA content (19.55 g/L) under optimal conditions, consisting of 3% palm oil mill effluent, with no additional trace elements, at 45oC and pH 7. The mutant strain showed higher resistance to substrate concentrations, as well as pH and temperature, than the wild type. The accumulation of PHA was increased by 3.18-fold compared to the wild type, and the production of PHA by the mutant M2-12 was constantly retained over 12 times of cultivation. The mutation and optimization strategy appear to be suitable for producing high density PHA, reducing the medium cost and consequently lowering the production cost. Interestingly, the mutant strain could synthesize the novel PHA copolymers such as 3-hydroxyvalerate and 3-hydroxyhexanoate, which were not produced by the wild type.

Laundry detergent-stable lipase from Pacific white shrimp (Litopenaeus vannamei) hepatopancreas: Effect of extraction media and biochemical characterization

ABSTRACT Extraction and biochemical properties of a new lipase from the hepatopancreas of Pacific white shrimp were studied. Recovery of the hepatopancreas powder with 50 mM Tris-HCl, pH 7.0 containing 0.2% (v/v) Brij35 gave a higher recovery of lipase activity than other extractants tested (p < 0.05). The optimal pH and temperature for lipase activity were 8.5 and 60°C, respectively, when p-nitrophenyl palmitate was used as a substrate. The enzyme was stable to heat treatment up to 40°C and over a pH range of 7.0–10.0 for 30–120 min. Lipase activities continuously decreased as the sodium deoxycholate (NaDC) concentration increased, but activities increased as NaCl concentration increased up to 3.0 M. Hydrolytic activity was enhanced by NaN3, but strongly inhibited by Hg2+, Cu2+, Al3+, and phenylmethanesulfonyl fluoride. The lipase was evaluated as highly stable against surfactants (Tween 20, Tween 80, Triton X-100, and gum arabic). However, the enzyme was unstable against sodium dodecyl sulphate. Stability of the lipase with commercial liquid and solid detergents (Attack®, Bres®, Omo®, and Pao®) was also investigated. The lipase exhibited substantial stability and compatibility with tested commercial liquid and solid laundry detergents for 30–60 min. The overall properties of the lipase from Pacific white shrimp hepatopancreas, thus leading us to propose that it is an excellent candidate for use as biocatalysts for better detergent formulation.

The production of polyhydroxybutyrate from liquid stillage and its application

The liquid stillage contained reducing sugars (fructose and glucose) and volatile fatty acids including acetic acid, propionic acid and butyric acid. 0.5 g/L of reducing sugar was found in raw stillage. Thereafter, ethanol was harvested and the stillage after ethanol recovery was utilized for polyhydroxybutyrate (PHB) production. The effect of stillage concentration, nitrogen source, temperature, agitation speed and initial pH were studied. The optimum condition for PHB production containing 50% of stillage with 5 g/L yeast extract as nitrogen source. The cultivation was incubated at 30°C under the agitation speed of 150 rpm and pH 7. The highest biomass (10.50±0.141 g/L) and PHB (5.75 g/L, 86.50±6.236% of dry cell weight, DCW) were obtained under optimum conditions. The PHB was further utilized for hydroxybutyrate methyl ester (HBME) production. The partial properties of HBME were studied.

The statistic optimization for lactic acid production by Lactobacillus Plantarum using ethanol stillage as sole carbon source

Optimization of medium composition and pH for lactic acid production byLactobacillus plantarum ATCC21028 were evaluated using statistical methods. Ethanol stillage, a liquid waste from refinery, was utilized as the sole carbon source. Complex interactions among concentrations of stillage (50-100%), yeast extract as a nitrogen source (0-5 g/L) and pH (4-9) were studied using central composite design (CCD) experiments. Using 50% of stillage in the presence of 2.5 g/L of yeast extract at pH 6.5 yield the highest lactic acid (94.68±0.006 mg/L), productivity (1.97 mg/L/h) and yield (0.128 mg/mg initial sugar). The optimum cultivation for the lactic acid production consisted of 50.003% of stillage and2.433 g/L of yeast extract at pH 6.537 (R2=0.999). The model was confirmed by culturing L. plantarumunder predicted conditions in a 5-L fermenter. The amount of lactic acid (94.24±0.018 mg/L) was not significantly different from the predicted value.