Protein enrichment of sweet potato residue with co-culture of amylolytic fungi by solid-state fermentation

Protein enrichment of sweet potato residue with amylolytic moulds by solid-state fermentation was higher than that obtained with amylolytic yeasts. The optimum initial moisture content for protein enrichment was 66% to 75%. Incrementally added nitrogen sources to the culture at zero time and at 24 h considerably improved the final protein content. During the cultivation, the moisture, ash and ATP contents increased, while the pH value decreased. A 1:1 co-culture of amylolytic mycelial fungi yielded a product with 32.4% crude protein after 4 days incubation at 30 degrees C.     

Protein enrichment of sweet potato residue by solid-state cultivation with mono- and co-cultures of amylolytic fungi

The degree of protein enrichment of sweet potato residue by different amylolytic moulds in solid-state cultivation was much greater than that obtained using amylolytic yeasts. The optimum initial moisture content for protein enrichment was about 65% (w/w). Adding nitrogen sources to the culture twice (at the start of the incubation and after 24 h) considerably improved the final protein content. A co-culture of amylolytic mycelial fungi yielded a product with 32% (w/w) crude protein after 4 days' incubation at 30°C. In a column reactor, the highest temperatures reached were 42°C and 40°C and the minimum O₂ concentrations were 1.5% and 2.5% of full saturation in the central and bottom layers, respectively.     

Tetracycline production with sweet potato residue by solid state fermentation

For saving energy in antibiotic production and reducing the amount of agricultural wastes, solid state fermentation was used in this study to produce tetracycline with sweet potato residue by Streptomyces viridifaciens ATCC 11989. It was found that the optimal media for tetracycline production were sweet potato residue 100 g, organic nitrogen (rice bran, wheat bran, or peanut meal) 20 g, (NH(4))(2)SO(4) 2.4 g, KH(2)PO(4) 0.4 g, CaCO(3) 1.8 g, NaCl 0.6 g, MgCl(2) 0.8 g, soluble starch 10 g, methionine 0.2 g, histidine 0.8 g, and monosodium glutamate 1.6 g with initial moisture content 68-72%, and initial pH 5.8-6.0. Each gram of dry weight substrate was inoculated with 1.0 x 10(8) conidia and incubated at 26 degrees C for 5-7 days, producing 4720 mug of total tetracycline equivalent potency. When incubated at 26 degrees C with the initial moisture content 68%, the conidia in solid media germinated on the second day, mycelia grew abundantly on the third day and reached stationary phase on the sixth day. The antibiotic production was consistent with the morphogenesis of S. viridifaciens: activity could be detected on the third day, had the maximal potency on the sixth day, and decreased slightly on the tenth day. (11-3-88 tly).     

Protein enrichment of sago starch by solid-state fermentation with Rhizopus spp.

Protein enrichment of sago starch of three different diameters was investigated both in flask culture and under forced aeration in a packed-bed fermenter using two strains of Rhizopus. Protein production by R. oligosporus UQM 145F was superior to Rhizopus sp. UQM 186F in the flask culture without aeration, with both preferring larger diameter (3 to 4 mm) spherical sago-beads. In the packed-bed fermenter with forced aeration, Rhizopus sp. UQM 186F led to more rapid protein production compared to R. ollgosporus UQM 145F and produced equivalent final yields (about 10% protein on a dry wt basis).E. Gumbira-Sa'id, P.F. Greenfield and D.A. Mitchell are with the Department of Chemical Engineering, and H.W. Doelle is with the Department of Microbiology, University of Queensland, Queensland 4072, Australia.     

Protein enrichment of potato processing waste through yeast fermentation

Potato starch obtained from waste waters of chips manufacturing was used as a fermentation substrate for yeast protein enrichment. Among 18 yeast strains, 6 strains were screened according to their biomass yield and protein content after fermentation for 16 h at 30 degrees C in an aerated glucose-based liquid media (4.5 Ls). Using concentrated media (25% solids) made from potato starch pre-hydrolyzed with malt flour and batch-fermented for 20 h at 26 degrees C under aerobic conditions, Candida utilis ATCC 9256 was the most efficient protein-forming strain. Scaled-up at the 100 Ls level, the aerobic batch process was improved under fed-batch conditions with molasses supplementation. After drying, fermented starch contained 11-12% protein, including 7-8% yeast protein.     

Oxytetracycline production byStreptomyces rimosus in solid state fermentation of sweet potato residue

Sweet potato residue, a starchy agricultural waste, was used as a substrate to produce oxytetracycline byStreptomyces rimosus TM-55 in a solid-state fermentation. Oxytetracycline was detected on the third day, reached its maximum value on the sixth day and remained constant to the twentieth day. Optimal conditions for oxytetracycline production were an initial pH of 5.5 to 6.5, supplemented with 20% (w/v) defatted roasted peanut meal, as the sole nitrogen source, 1.0% (w/v) CaCO₃ and 2.0% (w/v) MgSO₄·7H₂O, being incubated at 26 to 35°C for 6 to 7 days. Oxytetracycline reached 12.1 mg/g substrate.

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Résumé On a utilisé des résidus de patates douces, on résidu agricole amylacé, comme substral pour la production d'oxytétracycline parStreptomyces rimosus TM-55 par fermentation en milieu solide. On a détecté foxytétracycline le 3ème jour. Celui-ci a arteint sa concentration maximum le 6ème jour et celle-ci est restée constante jusqu'au 20eme jour. Les conditions optimales pour la production d'oxytétracycline sont les staivanies: un pH initial compris entre 5.5 et 6.5, l'ajout de 20% (p/v) de farine d'arachide dégraissée, comme seule source d'azote, 1.0% (p/v) de CaCO₃ et 2.0% (p/v) de MgSO₄.7H₂O, une température d'incubation de 26 à 35°C pendant 6 à 7 jours. On a aneint 12.1 mg d'oxytetracycline par g de substrat.

     

Potentialities and limitations of direct alcoholic fermentation of starchy material with amylolytic yeasts

Summary The fermentation characteristics of a large number of starch-degrading yeasts were compared. None of the amylolytic yeasts currently recognized, appear to be entirely suitable for direct alcoholic fermentation of starchy biomass. The species capable of extensive starch hydrolysis produce only low amounts of ethanol from glucose and dextrin, one of the major limitations being their low ethanol tolerances. Some of the less-active yeasts have much better glucosefermentation characteristics, but dextrin conversion is limited probably due to the nature of their enzyme systems. Using an -amylase dextrin (22.5% w/v), ethanol yields of about 70% were obtained with Saccharomyces diastaticus strains. Through associative fermentation of S. diastaticus and other selected amylolytic yeasts slightly better yields, however not exceeding 80%, were obtained.     

Protein measurement in solid-state fermentation

Summary Membrane filter culture was used as a model system for the investigation of the growth of Rhizopus oligosporus in solid-state fermentation. The biuret method gave more accurate estimations of protein than the Folin-Lowry method. However, due to the change in the protein content of the biomass during the fermentation, protein cannot be considered to be a reliable index of growth in solid-state fermentation.     

Production of extracellular debranching activity by amylolytic yeasts

Summary The production of extracellular pullulan-degrading enzymes by several amylolytic yeast strains was studied. The highest activity was obtained with species of Endomycopsis, Lipomyces, Filobasidium, Leucosporidium, and Trichosporon, and also with some amylase-hyperproducing mutants. The most active strains are potentially valuable partners for intergeneric protoplast fusion.     

Protein enrichment of grain sorghum by submerged culture of the amylolytic yeastsSchwanniomyces occidentalis andLipomyces kononenkoae

Cultivation of aSchwanniomyces occidentalis derepressed mutant in a 10% (w/v) gelatinized grain sorghum slurry increased the crude protein content of the biomass from an initial value of 12% to 41% (dry) within 20 h, with no detectable residual starch. Co-cultivation ofCandida utilis with theS. occidentalis mutant improved the final crude protein content to 47% within 18 h, whereas a co-culture ofC. utilis with aLipomyces kononenkoae mutant resulted in a cultivation time of 50 h with a significantly lower protein content and a low final -amylase activity. In a 15% (w/v) grain sorghum slurry aC. utilis/S. occidentalis co-culture increased the protein content to about 44% within 30 h. Yeast cultivation increased the lysine and threonine content of the final biomass considerably.     

A model for continuous fermentations with amylolytic yeasts

A two-stage, associative fermentation process is more effective for continuous yeast biomass production from starch than a single-stage mixed culture fermentation process. By operating two stages, competition for the same growth limiting substrate is reduced leading to efficient starch utilization. In this article, a mathematical model has been proposed for continuous, two-stage fermentation with a pure culture, amylolytic yeast in the first stage and a mixed culture second stage with a faster growing, nonamylolytic yeast. The model parameters were determined for Saccharomycopsis fibuligera and Candida utilis in continuous, single-stage, pure cultures. In the two-stage model, the effects of changes in dilution rate on biomass, amylase, reducing sugar, and starch concentration, and ratio of stage volumes on microbial composition are discussed and compared with experimental data.     

Protein enrichment of apple pomace by co-culture of cellulolytic moulds and yeasts

The co-culture of cellulolytic moulds and yeasts on apple pomace in solid-state fermentation (SSF) and liquid-state fermentation (LSF) increased the protein content of apple pomace. The co-culture of Candida utilis and Aspergillus niger was the best among several combinations and increased the protein content of dried and pectin-extracted apple pomace to 20% and 17%, respectively, under SSF conditions.The authors are with the Microbiology Research Laboratory, Department of Biosciences, Himachal Pradesh University, Shimia-171005, India.     

Xylose fermentation by yeasts

Summary Xylose reductase from the xylose-fermenting yeastPichia stipitis was purified to electrophoretic homogeneity via ion-exchange, gel and affinity chromatography. At physiological pH values the thermodynamic equilibrium constant was determined to be 0.575x10¹⁰ (l·mol^-1). Product inhibiton studies are reported which clearly show that the kinetic mechanism of the xylose reductase is ordered-bi-bi with isomerisation of a stable enzyme form.     

Xylose fermentation by yeasts

Summary Utilization and fermentation of xylose by the yeasts Pachysolen tannophilus I fGB 0101 and Pichia stipitis 5773 to 5776 under aerobic and anaerobic conditions are investigated. Pa. tannophilus requires biotin and thiamine for growth, whereas Pi. stipitis does not, and growth of both yeasts is stimulated by yeast extract. Pi. stipitis converts xylose (30 g/l) to ethanol under anaerobic conditions with high yields of 0,40 and it produces only low amounts of xylitol. The yield coefficient is further increased at lower xylose concentrations.Publication Nr. 2 of this series: Eur. J. Appl. Microbiol. Biotechnol. (1983) 17, 287–291.     

Reusing soy residue for the solid-state fermentation of Ganoderma lucidum

Lingzhi has been a popular oriental medicine used to treat various human diseases. Soy residue from the waste of tofu manufacturing was used to culture Ganoderma lucidum in solid-state fermentation. The solid-state fermentation was conducted in three types of containers: test tube, 500-ml flask, and sterilize-able polypropylene plastic bag. The highest rate of mycelial growth of 6 mm/day was observed in the medium of carbon/nitrogen (C/N) ratio of 80 using test tubes. However, a growth rate of 7.5 mm/day was found at the C/N ratio of 70-80 in the 500-ml flasks. In the tests using plastic bags, the fruiting bodies were fully developed only for the C/N ratios of 70 and 80. The components of fruiting bodies obtained from different media were also analyzed and compared. The contents of ash, polysaccharides, and crude protein of fruiting bodies were found higher in the media of C/N ratio of 80.     

Bioconversion of acid- and gamma-ray-treated sweet potato residue to microbial protein by mixed cultures

Sweet potato residue, a starchy agricultural waste, was used as a substrate to produce microbial protein by Fusarium moniliforme and Saccharomyces cerevisiae in submerged fermentation. Acid- and gamma-irradiation-pretreated sweet potato residue enhanced the biomass yield and protein production when the residue was fermented with F. moniliforme and S. cerevisiae. A mixed culture of F. moniliforme and S. cerevisiae efficiently and rapidly utilized free sugars; the maximal biomass yield (13.96 g/l) and protein production (65.8%) were obtained after 3 days fermentation. Lower carbon utilization by the two microbial strains occurred in the waste-containing media as compared to control, increasing the economic value of the waste usage. Received 25 October 2001/ Accepted in revised form 22 June 2002     

Co-producing lipopeptides and poly-gamma-glutamic acid by solid-state fermentation of Bacillus subtilis using soybean and sweet potato residues and its biocontrol and fertilizer synergistic effects

A Bacillus subtilis strain B6-1, previously isolated from the rhizosphere of vegetable, selectively produced antibiotics or poly-gamma-glutamic acid (gamma-PGA) in two kinds of liquid media and their co-productions were obtained when using soybean and sweet potato residues in solid-state fermentation. The antibiotics were purified and identified as fengycins. After these residue cultures were introduced, cucumber wilts were effectively suppressed. The introduction also significantly increased the dry weights of roots and shoots of cucumber seedlings, and the roots to shoots ratio, especially at lower nutrition, which indicated the fertilizer synergistic effects. So the product of soybean and sweet potato residues, cultivated with B6-1 co-producing lipopeptides and gamma-PGA, can be expected to be used as both biocontrol agents and fertilizer synergists.