Utilization of protein extract from dairy manure as a nitrogen source by Rhizopus oryzae NRRL-395 for l-lactic acid production.
Six levels of crude protein (0.21, 0.42, 0.84, 1.68, 2.52, and 3.36g/L) and six levels of protein hydrolysates from dairy manure, defined by degree of hydrolysis (DH, 6.9%, 17.2%, 25.9%, 33.8%, 36.1%, and 36.7%), were investigated as the nitrogen source for production of l-lactic acid by Rhizopus oryzae NRRL-395 with respect to the influence of nitrogen source on l-lactic acid yield and the correlation with biomass yield and mycelia morphology. Increases in crude protein from 0.21 to 1.68g/L led to an increase in l-lactic acid concentration in the culture media from 6.48 to 57.7g/L. However, further increases beyond 1.68g/L did not present continuing increases in l-lactic acid yields. The highest biomass yield was obtained at a crude protein nitrogen concentration of 2.52g/L. Hydrolysates with high DH resulted in high yields of l-lactic acid and biomass. At a nitrogen level of 0.42g/L (hydrolysates) with DH ranging from 33.8% to 36.7%, the l-lactic acid yield of 0.53-0.56g/g of glucose was achieved, coupled with a 13-14% yield of fungal biomass.
Yao
Wanying
W
Bioproducts and Biosystems Engineering Department, University of Minnesota, 1390 Eckles Avenue, St. Paul, MN 55108, USA.
Wu
Xiao
X
Zhu
Jun
J
Sun
Bo
B
Miller
Curtis
C
D000818:Animals; D018533:Biomass; D002417:Cattle; D003470:Culture Media; D003612:Dairying; D006868:Hydrolysis; D019344:Lactic Acid / Q000378:metabolism*; D008372:Manure; D009584:Nitrogen / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D012233:Rhizopus / Q000378:metabolism*
D003470:Culture Media; D008372:Manure; D011506:Proteins; D019344:Lactic Acid; D009584:Nitrogen