Experimental design of response surface methodology used for utilisation of palm kernel cake as solid substrate for optimised production of fungal mannanase

A closer look at the synthesis of 2-[18F]fluoroethyl tosylate to minimize the formation of volatile side-products

BACKGROUND

2-[¹⁸F]Fluoroethyltosylate ([¹⁸F]FEtOTs) is a well-known ¹⁸F-fluoroalkylating agent widely used to synthesize radiotracers for positron emission tomography. The widespread use of [¹⁸F]FEtOTs is due in part to its low volatility when compared to other halide and sulfonate building blocks. In this work, the radioactive volatile side-products formed during the synthesis of [¹⁸F]FEtOTs were identified and characterized for the first time, and an optimization of the reaction conditions to minimize their formation was proposed.

RESULTS

In order to characterize the volatiles produced during [¹⁸F]FEtOTs synthesis, the reaction mixtures of both cold FEtOTs and [¹⁸F]FEtOTs were co-injected onto the HPLC system. The radioactive peaks corresponding to the volatile compounds were collected, analyzed through headspace gas chromatography mass spectrometry sampler (HS-GC-MS) and identified as vinyl fluoride ([¹⁹F]VF) and 2-fluoroethanol ([¹⁹F]FEOH). By using a rotatable central composite design with a two-level full factorial core of two factors (2²), it was determined that temperature and time are independent variables which affect the generation of [¹⁸F]VF and [¹⁸F]FEOH during the radiosynthesis of [¹⁸F]FEtOTs. In addition, in order to reduce the formation of the volatiles ([¹⁸F]VF and [¹⁸F]FEOH) and increase the yield of [¹⁸F]FEtOTs, it was demonstrated that the molar ratio of base to precursor must also be considered.

CONCLUSION

[¹⁸F]VF and [¹⁸F]FEOH are volatile side-products formed during the radiosynthesis of [¹⁸F]FEtOTs, whose yields depend on the reaction time, temperature, and the molar ratio of base to precursor. Therefore, special care should be taken during the radiosynthesis and subsequent reactions using [¹⁸F]FEOTs in order to avoid environmental contamination and to improve the yield of the desired products.

The Purification and Biochemical Characterization of a Weissella cibaria F1 Derived β-Mannanase for Its Use in the Preparation of Konjac Oligo-Glucomannan with Immunomodulatory Properties

Mannanase with a molecular weight of 33.1 kDa was purified from Weissella cibaria F1. The F1 mannanase contained 289 amino acid residues and shared 70.0% similarity with mannanase from Bacillus subtilis (P55278 (MANB_BACIU)). The optimum reaction conditions of F1 mannanase were 50 °C and pH 6.5. After incubation at pH 4.5–8.0 and 30–60 °C for 2 h, the enzyme activity remained above 60%. The effects of metal ions on mannanase enzyme activity were measured, and Mn2+, Mg2+, and Cu2+ increased enzyme activity. The Km (16.96 ± 0.01 μmol·mL−1) and Vmax (1119.05 ± 0.14 μmol·min−1) values showed that the enzyme exhibited high affinity for locust bean gum. Mannanase was used to hydrolyze konjac glucomannan to produce konjac oligo-glucomannan (KOGM). KOGM increased the proliferation and phagocytosis of RAW264.7 macrophages and enhanced nitric oxide, and cytokine production in macrophages, which showed potent immunostimulatory activity. In this study, the advantages of mannanase derived from lactic acid bacteria were utilized to expand the application of KOGM in the medical field, which is helpful to explore the broad prospects of KOGM in functional food or medicine.

Biochemical Evaluation of Agaricus and Pleurotus Strains in Batch Cultures for Production Optimization of Valuable Metabolites

The production of various biochemical compounds such as proteins, glucans and glucanases, from the mycelium of four strains of Basidiomycetes species, Agaricus bisporus, Agaricus subrufescens, Pleurotus eryngii and Pleurotus ostreatus, during batch culture in shaking flasks, was studied. Fungi were cultured for 26 days in defined media with glucose as carbon source and were primarily evaluated for their ability to consume glucose and produce mycelial mass and intracellular polysaccharides (IPS). Results showed that on the 26th day of cultivation, P. ostreatus produced the maximum biomass (16.75 g/L), whereas P. eryngii showed the maximum IPS concentration (3.82 g/L). All strains presented a similar pattern in total protein production, with A. bisporus having the highest percentage of total proteins (36%, w/w). The calculated correlation coefficients among ribonucleic acid (RNA) vs. biomass (0.97) and RNA vs. protein (0.97) indicated a very strong relation between RNA and biomass/protein synthesis. The studied strains exhibited an increase in total glucan and glucanase (β-1,6) production during cultivation, with A. bisporus reaching the highest glucan percentage (8%, w/w) and glucanase activity (12.7 units/g biomass). Subsequently, processed analytical data were used in contour-graph analysis for data extrapolation to optimize future continuous culture.

Enhancement of β-Mannanase Production by Bacillus subtilis ATCC11774 through Optimization of Medium Composition

Palm kernel cake (PKC) has been largely produced in Malaysia as one of the cheap and abundant agro-waste by-products from the palm oil industry and it contains high fiber (mannan) content. The present study aimed to produce β-mannanase by Bacillus subtilis ATCC11774 via optimization of the medium composition using palm kernel cake as substrate in semi-solid fermentation. The fermentation nutrients such as PKC, peptone, yeast extract, sodium chloride, magnesium sulphate (MgSO₂), initial culture pH and temperature were screened using a Plackett-Burman design. The three most significant factors identified, PKC, peptone and NaCl, were further optimized using central composite design (CCD), a response surface methodology (RSM) approach, where yeast extract and MgSO₂ were fixed as a constant factor. The maximum β-mannanase activity predicted by CCD under the optimum medium composition of 16.50 g/L PKC, 19.59 g/L peptone, 3.00 g/L yeast extract, 2.72 g/L NaCl and 0.2 g/L MgSO₂ was 799 U/mL. The validated β-mannanase activity was 805.12 U/mL, which was close to the predicted β-mannanas activity. As a comparison, commercial media such as nutrient broth, M9 and Luria bertani were used for the production of β-mannanase with activities achieved at 204.16 ± 9.21 U/mL, 50.32 U/mL and 88.90 U/mL, respectively. The optimized PKC fermentation medium was four times higher than nutrient broth. Hence, it could be a potential fermentation substrate for the production of β-mannanase activity by Bacillus subtilis ATCC11774.

Production of mannooligosaccharides from various mannans and evaluation of their prebiotic potential

Aspergillus quadrilineatus endo-β-mannanase effectively degraded konjac glucomannan (66.09% w/v), copra meal (38.99% w/v) and locust bean galactomannan (20.94% w/v). High performance liquid chromatography (HPLC) analysis of KG hydrolysate indicated its mannooligosaccharides (MOS) content (656.38 mg/g) with high amounts of DP 5 oligosaccharide. Multi-scale characterization of mannan hydrolysate was done using FTIR and ¹³C NMR which revealed α and β form of galactose or glucose in MOS, respectively. CM and LBG hydrolysates (1 mg/mL) have shown cytotoxic effect and reduced cell viability of Caco-2 cells by 45% and 62%, respectively. MOS DP (1-4) derived from LBG supported better Lactobacilli biofilm formation as compared to KG hydrolysate containing high DP MOS (5-7). Lactobacilli effectively fermented MOS to generate acetate and propionate as main short chain fatty acids. Lactobacilli produced leucine, isoleucine and valine as branched chain amino acids when grown on LBG hydrolysate.

Enhancement of Versatile Extracellular Cellulolytic and Hemicellulolytic Enzyme Productions by Lactobacillus plantarum RI 11 Isolated from Malaysian Food Using Renewable Natural Polymers

Lactobacillus plantarum RI 11 was reported recently to be a potential lignocellulosic biomass degrader since it has the capability of producing versatile extracellular cellulolytic and hemicellulolytic enzymes. Thus, this study was conducted to evaluate further the effects of various renewable natural polymers on the growth and production of extracellular cellulolytic and hemicellulolytic enzymes by this novel isolate. Basal medium supplemented with molasses and yeast extract produced the highest cell biomass (log 10.51 CFU/mL) and extracellular endoglucanase (11.70 µg/min/mg), exoglucanase (9.99 µg/min/mg), β-glucosidase (10.43 nmol/min/mg), and mannanase (8.03 µg/min/mg), respectively. Subsequently, a statistical optimization approach was employed for the enhancement of cell biomass, and cellulolytic and hemicellulolytic enzyme productions. Basal medium that supplemented with glucose, molasses and soybean pulp (F5 medium) or with rice straw, yeast extract and soybean pulp (F6 medium) produced the highest cell population of log 11.76 CFU/mL, respectively. However, formulated F12 medium supplemented with glucose, molasses and palm kernel cake enhanced extracellular endoglucanase (4 folds), exoglucanase (2.6 folds) and mannanase (2.6 folds) specific activities significantly, indicating that the F12 medium could induce the highest production of extracellular cellulolytic and hemicellulolytic enzymes concomitantly. In conclusion, L. plantarum RI 11 is a promising and versatile bio-transformation agent for lignocellulolytic biomass.

Optimization of β-mannanase production by Bacillus subtilis US191 using economical agricultural substrates

The Bacillus subtilis US191 strain producing highly thermostable β-mannanase was previously selected as potential probiotic candidate for application as feed supplement in poultry industry. Initially, the level of extracellular β-mannanase production by this strain was 1.48 U ml^-1 . To improve this enzyme titer, the present study was undertaken to optimize the fermentation conditions through experimental designs and valorization of agro-industrial byproducts. Using the Plackett-Burman design, in submerged fermentation, a set of 14 culture variables was evaluated in terms of their effects on β-mannanase production. Locust bean gum (LBG), soymeal, temperature, and inoculum size were subsequently optimized by response surface methodology using Box-Behnken design. Under optimized conditions (1 g L^-1 LBG, 8 g L^-1 soymeal, temperature of 30°C and inoculum size of 10¹⁰  CFU ml^-1 ), a 2.59-fold enhancement in β-mannanase titer was achieved. Next, to decrease the enzyme production cost, the effect of partial substitution of LBG (1 g L^-1 ) by agro-industrial byproducts was investigated, and a Taguchi design was applied. This allowed the attaining of a β-mannanase production level of 8.75 U ml^-1 in presence of 0.25 g L^-1 LBG, 5 g L^-1 of coffee residue powder, 5 g L^-1 of date seeds powder, and 5 g L^-1 of prickly pear seeds powder as mannans sources. Overall, a 5.91-fold improvement in β-mannanase production by B. subtilis US191 was achieved.

Optimization of process conditions for tannin content reduction in cassava leaves during solid state fermentation using Saccharomyces cerevisiae

Cassava leaves are a crucial source of alternative protein resources for both humans and livestock in developing societies in African and Asian countries that do not have easy access to available protein sources. Hence, cassava has the capacity to promote the economic development of these countries and provide food security. However, it has some disadvantages due to the anti-nutrient compounds present in its tissues, which limits the nutritional value of cassava leaves. Thus, proper processing of cassava leaves is essential in order to reduce the anti-nutrients to a safer limit before utilization. This study focuses on reducing the tannin content of cassava leaves during solid-state fermentation using Saccharomyces cerevisiae. In addition, the Box-Behnken design of the Response Surface Methodology was applied to optimize various process parameters, such as carbon concentration, nitrogen concentration, moisture content, and incubation time for maximum reduction of tannin content in cassava leaves. A quadratic model was developed for the reduction of tannin content, which resulted in a perfect fit of the experimental data (p < 0.01). The optimal conditions were found at 1.4% (w/w) of carbon concentration, 0.55% (w/w) of nitrogen concentration, 57% (v/w) moisture content, and an incubation time of 96 h. The minimum tannin content obtained under these conditions was 0.125%, which indicated a reduction of 89.32 % in tannin content. Conversely, the protein content was increased with a further increase in fermentation time from 24 to 96 h (from 10.08 to 14.11-16.07 %). Furthermore, the ability of Saccharomyces cerevisiae to produce tannase under solid-state fermentation of cassava leaves was also studied. The maximum yield was obtained with an enzyme activity of 0.53 U/gds after 72 h of incubation.

Production optimization and characterization of mannooligosaccharide generating β-mannanase from Aspergillus oryzae

A multi-tolerant β-mannanase (ManAo) was produced by Aspergillus oryzae on copra meal, a low-cost agro waste. Under statistically optimized conditions, 4.3-fold increase in β-mannanase production (434 U/gds) was obtained. Purified ManAo had MW ∼34 kDa and specific activity of 335.85 U/mg with optimum activity at 60 °C and at pH 5.0. Activity of ManAo was enhanced by most metal ions and modulators while maximum enhancement was noticed with Ag⁺ and Triton X-100. K_m and V_max were 2.7 mg/mL and 1388.8 µmol/min/mg for locust bean gum while the enzyme showed lower affinity towards konjac gum (8.8 mg/mL, 555.5 µmol/min/mg). Evaluation of various thermodynamic parameters indicated high-efficiency of the ManAo with activation energy 12.42 KJ/mol and 23.31 KJ/mol towards LBG and konjac gum, respectively. End product analysis of β-mannanase action by fluorescence assisted carbohydrate electrophoresis (FACE) revealed the generation of sugars from DP 1-4 with some higher DP MOS from different mannans.