Effect of dissolved oxygen concentration and impeller tip speed on itaconic acid production by Aspergillus terreus

Summary Effect of aeration rate and impeller tip speed on mycelium growth and itaconic acid production was investigated in a batch culture of Aspergillus terreus IFO-6365. When impeller tip speed was 94.2 cm/sec at a fixed aeration rate of 0.5 vvm, itaconic acid concentration was 3.6 and 1.6 times higher than those in the impeller tip speed of 62.8 and 125.7 cm/sec, respectively. When an oxygen-enriched air was supplied at a fixed impeller tip speed of 94.2 cm/sec and dissolved oxygen concentration was maintained in the 20–60 % range, both itaconic acid concentration and mycelium growth were not affected by the dissolved oxygen concentration.     

Influence of formaldehyde in control of bacterial and fungal contaminants in plant cell cultures: Its effect on growth and secondary metabolite production

Summary Influence of formaldehyde on growth and secondary metabolite production inin vitro grown tissues of pyrethrum, capsicum and carrot were studied. Formaldehyde concentration above 0.025% completely inhibited the growth of addedBacillus andAspergillus in the culture medium. Formaldehyde up to 0.025% level caused slight inhibition in the growth of pyrethrum callus. Callus subjected to 0.05, 0.1 and 0.2% formaldehyde enhanced the level of pyrethrin production in pyrethrum callus, whereas production of phenolics was lower in all the treatments. Growth of carrot callus and anthocyanin production was not inhibited up to a formaldehyde concentration of 0.04%. Similarly, the production of capsaicin in immobilised cell cultures ofCapsicum frutescens was not inhibited up to 0.04% level of formaldeyde. The results demonstrate the usefulness of formaldehyde to control contamination in plant tissue culture.     

Reactor kinetics for submerged aerobic biofilms

Sclerotium rolfsii ATCC 15205 was cultivated in continuous culture (48 l reactor volume) for scleroglucan production. The maximum volumetric productivity (Q_Pvmax) amounted to 7.2 g/ld and was more than twice as high as in comparable batchwise cultivations. In addition, the relation between (a) volumetric productivity (Q_P [g/ld]) and product yield (Y_{Glucan/Glucose} [1]), (b) volumetric productivity and product quality (M_W [g/mol]), and (c) product quality and impeller tip speed (Nd [m/s]) was studied in continuous culture. It was found, that an increase in volumetric productivity led to a decline in product yield and product quality. Furthermore, an impeller tip speed of >0.7 m/s decreased the attainable product quality considerably. Based on these results, the impact of the operational setpoint of the process in terms of oxygen supply and reactor scale on the economics of scleroglucan production was discussed. In contrast to batchwise cultivation, scleroglucan production in continuous culture proved to be not feasible under non-aseptic conditions.     

Production of L-DOPA from cell suspension culture of Mucuna pruriens f. pruriens

Summary Production of L-DOPA was studied in cell suspension culture of Mucuna pruriens f. pruriens. Suspension culture was established in MSI medium composed of half concentration of Murashige and Skoog's salts and 2% sucrose. A two-stage cell suspension culture was developed for enhanced accumulation of L-DOPA. In the first stage, the culture system was composed of MSI medium without CaCl, which was suitable for cell growth and in the second stage MSI medium containing 42.5 mg.l^–1 KH₂PO₄ and 4% sucrose favoured L-DOPA production. A discernible higher production of L-DOPA was obtained in this two-stage cell suspension culture in comparison to single stage culture.     

Exogenous hormone applications at pollination for in vitro and in vivo production of cotton interspecific hybrids

Interspecific hybridization of cotton (Gossypium) has been assisted by ovule and embryo culture. These culture methods were compared to exogenous hormone applications for efficient plant production from crosses between Upland cotton, G. hirsutum L., as the maternal parent, and various diploid and tetraploid wild species as the pollen donor. The best exogenous hormone treatment resulted in an average production of five seeds per boll and 4% boll abscission. Generally, exogenous hormones used with standard hybridization techniques were superior to in vitro methods, but for some crosses, embryo culture following hormone applications was warranted.Abbreviations GA gibberellic acid, >90% A₃ - NAA 1-naphthaleneacetic acid - NOA 2-naphthoxyacetic acid.     

N-carboxymethylchitosan inhibition of aflatoxin production: Role of zinc

Aqueous Solutions of N-carboxymethylchitosan (NCMC) suppressed both growth and aflatoxin production byAspergillus flavus andA. parasiticus in submerged culture (Adye and Mateles A&M). Test media were amended with various concentrations of zinc (15, 30, 45, 60 uM), and NCMC solution (0.62 uM). After 8 days incubation NCMC-treated cultures showed marked reduction of aflatoxin production and fungal growth. Enhanced levels of zinc did not overcome the NCMC-mediated inhibition of fungal growth or aflatoxin production.     

Azadirachtin production in stirred tank reactors by Azadirachta indica suspension culture

Successful scale-up of Azadirachta indica suspension culture for azadirachtin production was done in stirred tank bioreactor with two different impellers. The kinetics of biomass accumulation, nutrient consumption and azadirachtin production of A. indica cell suspension culture were studied in a stirred tank bioreactor equipped with centrifugal impeller and compared with similar bioreactor with a setric impeller to investigate the role of O₂ transfer efficiency of centrifugal impeller bioreactor on overall culture metabolism. The maximum cell mass for centrifugal impeller bioreactor and stirred tank bioreactor (with setric impeller) were 18.7 and 15.5 g/L (by dry cell weight) and corresponding azadirachtin concentrations were 0.071 and 0.05 g/L, respectively. Glucose and phosphate were identified as the major growth-limiting nutrients during the bioreactor cultivation. The centrifugal impeller bioreactor demonstrated less shearing and improved O₂ transfer than the stirred tank bioreactor equipped with setric impeller with respect to biomass and azadirachtin production.     

Partial characterization of anEscherichia coll strain harboring a xylanase encoding plasmid

Summary The plasmid pRH271, harboring a xylanase gene cioned fromBacilius subtilis, has been transferred into a mutant ofE. coli SK2284 which allowed the release of part of the xylanase in the culture supernatant. Kinetic parameters of this recombinantE. coll strain were determined in microscale batch culture with and without the selective pressure of antibiotics. No significant difference in µ_max was observed for the nontransformedE. coli strain when compared to the recombinant strain. However, K₅ values for glucose were two times higher in the case of the recombinant strain. Preliminary study of xylanase production in a large batch farmenter was also described.     

Lipase production byCandida rugosa: Fermentation behaviour

Summary Extracellular lipase production byCandida rugosa growth has been studied. The main growth parameters, and the lipase activity in the culture broth were determined in order to identify the maximum of enzyme activity.The effect of lipidic material and size and growth phase of the inoculum on enzymatic production have been studied. Maximum extracellular lipase activity was associated with an increase in enzyme production when the number of viable cells started to decrease.     

Recovery of megakaryocyte thromboxane production in vitro after aspirin inhibition

Megakaryocytes isolated in high purity from guinea pigs produced thromboxane B₂ in response to exogenously provided arachidonic acid. This production was inhibited by in vitro treatment with acetylsalicylic acid with a concentration response relationship similar to that seen in platelets. During in vitro culture, the aspirin-treated megakaryocytes recovered thromboxane synthetic ability. Following a lag of 12 hours, recovery of megakaryocyte thromboxane production resumed at a rate of 16% of control per day. This recovery was inhibited by the addition of cycloheximide to the culture medium.     

Elicitation of anthocyanin production in cell cultures of carrot (Daucus carota L) by using elicitors and abiotic stress

Summary A cell line of carrot (Daucus carota L) which produces anthocyanin was subjected to various elicitors and abiotic stresses: The elicitors tested were culture filtrates (CF) and cell extracts (CE) of certain bacteria and yeasts. The abiotic stresses were salts of certain metal ions. The production increase obtained with cell extracts of Bacillus cereus. Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus were 49, 72, 45 and 41% respectively over the control. Maximum elicitation was obtained with elicitor derived from cell extract of the yeast Rhodotorula rubra where it enhanced anthocyanin production by two fold. The abiotic stress agents Ca, Mn, Zn, Co, Fe & V enhanced anthocyanin production. Of all the metal ions tested Ca was the most effective. The elicitation process was governed by the type and level of elicitor.     

Expression ofBacillus subtilis endoglucanase gene inLactobacillus acidophilus

Summary ABacillus subtilis gene which codes for endoglucanase was transferred intoLactobacillus acidophilus by electroporation with plasmids containing the gene. The endoglucanase gene expressed well in the transformed cells and most of the gene product was found in the culture medium. The efficiency of the endoglucanase production by the transformed.L. acidophilus cells depended greatly on the choice of the vector plasmids on which the gene to be inserted.     

Amylase production byEscherichia coli immobilized in silicone foam

Summary Silicone foam was investigated as a support for the immobilization ofEscherichia coli EC147, a recombinant strain which produces a thermostable amylase extracellularly. While colonization of the foam was limited in semicontinuous culture, a fivefold increase in amylase production was achieved.     

Development of media for growth ofDioscorea Deltoidea cells andin vitro diosgenin production: Influence of media constituents and nutrient stress

Summary Callus culture ofDioscorea deltoidea produced diosgenin and sterols during stationary phase. Ammonium nitrate (420 mg Nitrogen/l) as sole nitrogen source supported better growth than a combination of ammonium nitrate and potassium nitrate (totally equivalent to 840 mg Nitrogen/l). The production of diosgenin increased under low phosphate concentration (100 mg/l) whereas high phosphate concentration (240 mg/l) promoted growth. Micronutrients, when used at 1 1/2 strength, enhanced growth and diosgenin production. Depletion of nitrogen increased the diosgenin synthesis by a factor of 2. Adoption of a two stage culture method enhanced the diosgenin production in cultured cells by eight-fold.     

Alkaloid production in cell suspension cultures of Thalictrum flavum and T. dipterocarpum

Both cell suspension cultures of Thalictrum flavum and T. dipterocarpum were found to produce berberine (0.3 and 0.4 g/l, respectively) as a main alkaloid. Berberine production in the latter was markedly stimulated by 1-naphthaleneacetic acid in combination with 6-benzylaminopurine, whereas it was rather suppressed by the same auxin in the former. T. flavum cultures accumulated berberine and columbamine in the cells without releasing them into medium. On the other hand, T. dipterocarpum cultures released berberine into medium during the logarithmic growth phase, but thereafter accumulated all the berberine synthesized in the cells.Abbreviations LS Linsmaier and Skoog - 2,4-D 2,4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid - BA 6-benzylaminopurine - TFG a culture strain of T. flavum ssp. glaucum - TDP a culture strain of T. dipterocarpum     

Isolation and characterization of a symbiotic cellulolytic mixed bacterial culture

Summary By using batch-culture enrichment techniques a mixed culture of two bacterial spe cies identified as Cellulomonas flavigena and Xanthomonas sp was isolated. The capacity of both bacteria to grow as pure cultures in a min eral medium with alkaline pretreated sugar cane bagasse or cellobiose was tested. C. flavigena as pure culture was able to grow on both substrates only when yeast extract or biotin and thiamine were added to the culture medium, while Xanthomonas sp. could not grow on sugar cane ba gasse, but assimilated cellobiose if yeast extract was supplied. However, both bacteria in mixed culture grew very well on both substrates and did not require any growth factor. It was concluded that the interaction was favourable to both species. The mixed culture had the capacity to degrade a number of different agricul tural wastes and to use them as the sole carbon and energy source for the production mainly of biomass. More than 80% of pineapple bagasse, without chemical pretreatment, was used up by the microbial system.     

Production of shikonin derivatives by cell suspension cultures of Lithospermum erythrorhizon

A two-layer culture method was established that uses an organic solvent to remove shikonin derivatives produced on cell surfaces during the culture of suspension cells of Lithospermum erythrorhizon. Some paraffins and a fatty acid ester made suitable solvents, whereas olefins and aromatic solvents extensively inhibited the production of shikonin derivatives. The yield of derivatives increased with an increase in the carbon chain length of the n-paraffin used as the solvent and when the oxygen supply was sufficient it reached the value found for the ordinary culture method.     

Hyperproduction of N-acetylneuraminate lyase by the gene-cloned strain ofEscherichia coli

Summary Optimal culture medium for production ofN-acetylneuraminate lyase (NANA lyase) by the gene-cloned strain ofEscherichia coli, E. coli(pNALl), was screened to develop the process for the industrial production of NANA lyase. Out of nutrients tested, corn steep liquor (CSL) and sugarcane molasses were superior nutrient sources for the enzyme production. Hyperproduction (6–8 units/ml-broth) was achieved on the medium consisted of CSL and molasses.     

Diacetyl production by co-immobilized citrate-positiveLactococcus lactis subsp.lactis 3022 and homogenized bovin liver in alginate fibers with double gel layers

Summary Diacetyl production by (Citr⁺)Lactococcus lactis subsp.lactis 3022 cells immobilized in Ca-alginate fine fibers with single layer in the presence of catalase was three times higher than that in the absence of catalase. A co-immobilized culture system of the lactic acid bacterial cells (outer) and the homogenized bovine liver (inner layer) in Ca-alginate fibers with double gel layers was developed. The culture system gave high diacetyl productivity (30 mg/l) for ten repeated batch cultures.     

Visual detection of β-fructofuranosidase (inulase) —Regulatory mutants ofKluyveromyces fragilis

Summary Inulase constitutive mutant cells of the yeastKluyveromyces fragilis were enumerated in continuous culture cell populations. After cloning and growth on glycerol agar plates, mutant colonies stained red when exposed to a mixture of sucrose and a chromogenic reagent for glucose.Mutants with improved inulase production on glucose were isolated from opaque agar plates containing undissolved inulin. Mutant colonies were surrounded with clearing zones. Attempts to isolate similar mutants by selection for 2-deoxyglucose resistance proved unsuccessful withK. fragilis.