Release of soluble phosphorus through biodegradation of poultry litter by Bacillus subtilis.

The mineral content of two types of poultry litter; that is from meat producing chickens (broilers)  and from egg laying chickens (layers) was investigated. The egg poultry litter was superior to meat  poultry litter in the mineral composition, and its mineral content (% DW) was P 3.5, K 3, Ca 9, N  2.4, Mg 0.5, and Fe 1.2 in addition to moderate levels of Mn, Zn, Cu and Mo. The litter content of the toxic heavy metals was small; ranging from 2.6 ppm (mg kg-1) for Cd and 7.4 ppm for Pb to  relatively high levels of As (36.3 ppm). The microbial content of egg poultry litter was dense and amounted to 2×106 Colony Forming  Unit (CFU) per g dry litter, distributed among twenty four bacterial isolates and seven isolates of actinomycetes; and the bacterial isolates were sorted into twenty-one Gram positive endospore-forming rods and three Gram negative rods. Each of the twenty four bacterial isolates were incubated with sterile egg poultry litter and the release of inorganic phosphorus (Pi) was monitored over time for a period of 20 days. Out of the 24 bacterial isolates three exhibited outstanding ability to release Pi from litter; and from these three isolates, one was selected for further cultural, microscopic and physiological investigations, and was identified as Bacillus subtilis. Upon incubation of Bacillus subtilis with litter the yield of Pi increased progressively with time from an initial value of 0.86 mg Pi g-1 litter to 2.17 mg Pi g-1 litter by the fifteenth day, beyond which it leveled off up to the twentieth day.

Keywords: Arsenic, Bacillus subtilis, biodegradation, phosphorus, poultry litter.