Biomedical subjects

R A Sparringa

Publications and source records attributed to R A Sparringa.

3 recordsLinked to original sources

PubMed2002

Effects of temperature, pH, water activity and CO2 concentration on growth of Rhizopus oligosporus NRRL 2710.

AIMS: To investigate the effects of temperature, pH, water activity (aw) and CO2 concentration on the growth of Rhizopus oligosporus NRRL 2710. METHODS AND RESULTS: Hyphal extension rates from mycelial and spore inocula were measured on media with different aw (approximately 1.0, 0.98 and 0.96) and pH (3.5, 5.5 and 7.5) incubated at 30, 37 or 42 degrees C in atmospheres containing 0.03, 12.5 or 25% (v/v) CO2. The effects of environmental conditions on hyphal extension rate were modelled using surface response methodology. The rate of hyphal extension was very sensitive to pH, exhibiting a pronounced optimum at pH 5.5-5.8. The hyphal extension rate was less sensitive to temperature, aw or CO2, exhibiting maximum rates at 42 degrees C, a(w) approximately 1.0 and 0.03% (v/v) CO2. CONCLUSIONS: The fastest hyphal extension rate (1.7 mm h(-1)) was predicted to occur at 42 degrees C, pH 5.85, a(w) approximately 1.0 and 0.03% CO2. SIGNIFICANCE AND IMPACT OF THE STUDY: The present work is the first to model the simultaneous effects of temperature, pH, aw and CO2 concentration on mould growth. The information relates to tempe fermentation and to possible control of the microflora in Tanzanian cassava heap fermentations.

Carbon Dioxide↗

PubMed1999

Glucosamine content of tempe mould, Rhizopus oligosporus.

The glucosamine content of Rhizopus oligosporus NRRL 2710 mycelium grown in different media was determined. In Sabouraud dextrose broth the glucosamine content ranged from 51 g (kg dry biomass)(-1) for mycelial pellets less than 5 mm diameter to 107 g kg(-1) for pellets 16-35 mm diameter. Mycelium grown on Sabouraud dextrose agar contained 111 g glucosamine (kg dry biomass)(-1) while that grown on soymilk agar, used to simulate growth on soybeans in tempe, contained 82 g kg(-1). The estimation of glucosamine was reproducible, with a mean coefficient of variation of 4% for mycelial pellets and 11% for mycelium from agar media. It is suggested that a conversion factor of 12 g dry biomass (g glucosamine)(-1) is applicable to determine fungal biomass in tempe fermentation.

Biomass↗

PubMed1999

Protein utilization during soybean tempe fermentation.

The aim was to identify to what extent proteins were utilized during the fermentation of bacteria-free tempe prepared with acidified soybean cotyledons and Rhizopus oligosporus NRRL 2710 at 30 degrees C. Dry matter declined continuously during the fermentation to 980 g/(kg of initial dry cotyledons) at 28 h, 910 g at 46 h (when the tempe was judged mature), and 835 g at 72 h. The decrease in dry matter was due mainly to reduction in crude lipid, amounting to 65 g/(kg of initial dry cotyledons) at 46 h and 135 g/(kg of initial dry cotyledons) at 72 h and representing approximately 70% and 80%, respectively, of the total dry matter loss. Protein oxidation (estimated from ammonia production) was 5 g at 28 h,10 g at 46 h, and 20 g/(kg of initial dry cotyledons) at 72 h. The total amount of soy protein hydrolyzed, including that incorporated into mold biomass, was estimated to be 80 g/(kg of initial dry cotyledons) at 28 h incubation, 95 g at 46 h, and 100 g at 72 h. The hydrolyzed protein at 46 h represented 25% of the initial protein. Of this hydrolyzed protein, it is suggested that approximately 65% remained in the tempe as amino acids and peptides, 25% was assimilated into mold biomass, and 10% was oxidized.

Fermentation↗