Factors affecting production of mold mycelium and protein in synthetic media

Abstract

The effects of certain cultural conditions on the yield of dry mycelium, protein, and total amino acid content of Rhizopus oligosporus Saito (NRRL 2710), Rhizopus rhizopodiformis (Cohn apud Lichtheim) Zopf (NRRL 6246), and Absidia corymbifera (Cohn) Sacc. et Trotter (NRRL 6247) were studied. The yield of mycelium was found to significantly increase as the spore inoculum was increased from 187,500 to 2,250,000 spores. But the total amino acids (grams/liter) did not change significantly, whereas the percentage of crude protein decreased. An inoculum containing approximately 750,000 spores/ml was used in all of the other experiments. Mycelial production was highest at 37°C for all three molds. However, the best temperature for percentage of crude protein and total amino acids varied with the organism. The mycelial yield and total crude protein ofR. oligosporus showed some significant changes as the C/N ratio was increased in 3% glucose medium. In a synthetic medium having a 15:1 C/N ratio, the strains of R. oligosporus, R. rhizopodiformis, and A. corymbifera had better yields of dry mycelium with glucose than with galactose and sucrose as carbon sources. However, in media having a 7:1 C/N ratio and optimum pH, R. oligosporus showed better yields from galactose than glucose, not only in dry mycelium but also in total crude protein (grams/liter) and total amino acids (grams/liter). R. oligosporus grew very well on several ammonium salts, but the maximum yield of dry mycelium, total crude protein (grams/liter), and total amino acids (grams/ liter) occurred with ammonium sulfate. The optimum pH for both Rhizopus species was 4.0, althoughR. oligosporus grew equally well at pH 3.0 and slightly less at pH 5.0. The highest yield of mycelium for A. corymbifera was obtained in a medium with an initial pH of 8.0. It was calculated that a fermenter charged with an adequate medium and 1,000 lb (about 450 kg) of R. oligosporus or A. corymbifera cells could produce 88 or 90 lb of protein (on a dry-weight basis) per h if the product was removed continuously.

From stale bread and brewers spent grain to a new food source using edible filamentous fungi

“…SSF on rice bran and N. intermedia SSF on okara due to fungal lipase activity for biomass production [ 73 – 75 ]. The increase in the total lipid content may be due to the fact that a high concentration of carbohydrate in stale bread favors the production of mycelial fat [ 76 ] or, as stated by Beuchat and Worthington [ 77 ], due to the selective utilization of non-lipid materials during cultivation. The fungus N. sitophila , among other fungi, was reported by the same authors to not utilize lipids during SSF of full-fat peanuts and preferential utilization of free fatty acids was not detected during the cultivation phase.…”

Converting corn wet‐milling effluent into high‐value fungal biomass in a biofilm reactor

“…Figure 1b shows the schematics of the fungal biofilm reactor. Graham et al (1976) reported that the maximum yield of R. microsporus was obtained at a temperature of 378C and pH ranging from 3.0 to 5.0. Previous studies on suspended growth systems also showed that these parameters are optimal for fungal growth (Jin et al, 1999b;Van Leeuwen et al, 2003).…”

“…Since the availability of macro-and micro-nutrients has been reported to greatly impact fungal growth and survival (Moore-Landecker, 1996) and the corn wet-milling effluent had a low macro-nutrient content [nitrogen (N) and phosphorus (P)], additional N as (NH 4 ) 2 SO 4 and P as KH 2 PO 4 were added aseptically to the feed to maintain a COD:N:P ratio of 100:5:1, a typical ratio for biological growth. Trace metals, such as magnesium, iron and zinc were also supplied as suggested by Graham et al (1976).…”

Ozone as a selective disinfectant for nonaseptic fungal cultivation on corn-processing wastewater

“…Different microorganisms consume specific _substrates at different rates due to their diverse metabolisms (Wainwright 1992). For example, Graham et al (1976) determined the yield of R. oligospo~us, l~hizopus fo~mis, and Aspe~gillus co~ymbife~a on different substrates and found that yield varied based on the microbial preferences (Table 2.8}.…”