Busaba Yongsmith

Production of yellow pigments in submerged culture of a mutant of Monascus spp.

Abstract This paper communicates our new findings on a mutant of Monascus mold which is capable of producing a high concentration of yellow pigments (λ max 370 nm) instead of red pigments (λ max 420 and 500 nm) produced by its parents strains. Various factors affecting yellow pigment production have been examined. It was found that the mutant produced the maximal amount of pigment under the optimal conditions for pigment production of its parent strains. The mutation allowed a 10-fold increase in both yellow pigment production and amylolytic enzyme activity over those from a yellow pigment producer isolated previously by us.

Color mutants of Monascus sp. KB9 and their comparative glucoamylases on rice solid culture

Abstract Monascus sp. KB9 strain was used to convert carbohydrate base agricultural commodities to value added pigments. Mutagenesis of this strain using UV light and successive isolation was found to improve the yield of pigment product. As a result, two hyper pigment productive strains, red and yellow mutants were obtained. In addition, one white mutant was also obtained. These color mutants together with their parental strain were used to compare glucoamylase production in rice solid culture. Initial moisture content of rice at 35–43% is found to affect glucoamylase of these four strains. It is noteworthy that the white mutant which lost its ability to produce pigment and revealed morphology indifference to its parental strain could produce the highest glucoamylase enzyme at 4.07×105 U/gdw (units per gram-dry weight). This is about 3, 7, and 16 times higher than the wild type strain, red, and yellow mutants, respectively. The crude enzyme showed its thermophilic property at optimal temperature, 65°C, and its optimal pH, 4.7.

Production of vitamin B12 by immobilized cells of a propionic acid bacterium

SummaryThe ability of immobilized cells of propionic acid bacteria to form vitamin B12 has been investigated. Propionibacterium arl AKU 1251 having a considerable activity to produce the vitamin was selected as a test organism among six strains of propionic acid bacteria tested. The whole cells were entrapped with urethane prepolymers, photo-crosslinkable resin prepolymers or several other materials such as κ-carrageenan, agar or sodium alginate, and their vitamin B12 productivity was compared. Based on the criteria of the convenience of preparation and the stability of the cell-entrapping gels, a hydrophilic urethane prepolymer, PU-9, was employed as gel material. Satisfactory vitamin B12 production was obtained when 5–10 g of wet cells precultured to the late exponential growth phase were entrapped with 1 g of the prepolymer. Addition of a suitable amount of cobaltous ion and of 5,6-dimethyl benzimidazole to the culture medium was effective for the production of the vitamin by the immobilized cells. The repeated use of the immobilized cells was successfully achieved when a suitable amount of cells were entrapped and allowed the proliferation of cells inside gel matrices.

Maximizing yellow pigment production in fed-batch culture of Monascus sp.

Yellow pigment production in exponential fed-batch cultivation of Monascus sp. was studied. Due to the difficulty of measuring the optical density for accurate determination of the cell concentration, a capacitance probe was employed on-line. The feed rate needed to keep the specific growth rate, mu, constant in fed-batch culture was determined on the basis of the cell concentration measured by the capacitance probe. Control of mu was improved by using updated information on the cell concentration compared with the simple feed-forward determination method using the initial cell concentration only. The highest specific pigment production rate was achieved with a mu of 0.02 h(-1) in the feeding phase. However, among several fermentation examined, the largest pigment production in the final step was obtained at a mu of 0.01 h(-1); in each case the same amount of substrates was used. An investigation of the optimal initial glucose concentration revealed that pigment production was maximum when the initial glucose concentration in the batch mode was 10 g/l and mu was 0.01 h(-1) in the fed-batch mode. It was also found that the pellet weight in the fermentation could be accurately estimated by image analysis. The ratio of the mycelium weight to the total cell weight estimated from information on the total cell weight and the estimated pellet weight was found to be more than 80%. However, no clear quantitative relationship could be discerned between the specific pigment production rate, rho, and the ratio of mycelium in the cell population.

Enhancement of yellow pigment production by intraspecific protoplast fusion of Monascus spp. yellow mutant (ade(-)) and white mutant (prototroph).

To breed industrially useful strains of a slow-growing, yellow pigment producing strain of Monascus sp., protoplasts of Monascus purpureus yellow mutant (ade(-)) and rapid-growing M. purpureus white mutant (prototroph) were fused and fusants were selected on minimal medium (MM). Preliminary conventional protoplast fusion of the two strains was performed and the result showed that only white colonies were detected on MM. It was not able to differentiate the fusants from the white parental prototroph. To solve this problem, the white parental prototroph was thus pretreated with 20mM iodoacetamide (IOA) for cytoplasm inactivation and subsequently taken into protoplast fusion with slow-growing Monascus yellow mutant. Under this development technique, only the fusants, with viable cytoplasm from Monascus yellow mutant (ade(-)), could thus grow on MM, whereas neither IOA pretreated white parental prototroph nor yellow auxotroph (ade(-)) could survive. Fifty-three fusants isolated from yellow colonies obtained through this developed technique were subsequently inoculated on complete medium (MY agar). Fifteen distinguished yellow colonies from their parental yellow mutant were then selected for biochemical, morphological and fermentative properties in cassava starch and soybean flour (SS) broth. Finally, three most stable fusants (F7, F10 and F43) were then selected and compared in rice solid culture. Enhancement of yellow pigment production over the parental yellow auxotroph was found in F7 and F10, while enhanced glucoamylase activity was found in F43. The formation of fusants was further confirmed by monacolin K content, which was intermediate between the two parents (monacolin K-producing yellow auxotroph and non-monacolin K producing white prototroph).

Bioenrichment of Vitamin B12 in Fermented Foods

Vitamin B12 (cobalamins) is important for nutrition and health but it cannot be synthesized by plants or animals. Vitamin B12 enrichment in some vegetarian diets by the safe bacteria have been developed and presented.

Traditional Fermented Foods in Thailand

There are many traditional fermented foods in Thailand, with almost a hundred kinds. The history of Thai fermented foods dated back to more than a century ago as an art without any scientific information support. The knowledge and experiences of Thai fermented products were handed down from generation to generation with successful or unsuccessful due to spontaneous fermentation. Two decades ago, scientists and researchers in Thailand were concerned on key microorganisms involved and how to make a consistent quality product which lead to the application of starter culture in various products. In this article, two main categories of Thai traditional fermented foods are presented which are salted and non-salted products, and the raw materials ranged from fish, meat, fruit, vegetable, rice, etc. The key microorganisms found in such products included beneficial ones such as lactic acid bacteria, yeast, and fungi. In addition, the development and future trend of Thai traditional fermented foods were proposed in order to improve the quality and safety of products and also extend for scale-up production.