Lactulose production from milk concentration permeate using calcium carbonate-based catalysts

Milk concentration permeate (MCP), a low-value by-product of ultrafiltration plants and calcium carbonate-based catalysts were used for lactulose production. The results obtained show the effectiveness of oyster shell powder and limestone for lactose isomerisation as a replacement for egg shell powder. With the reaction conditions of 12 mg/ml catalyst loading, reflux time of 120 min at 96 °C, a maximum yield of 18–21% lactulose was achievable at a cost of <50% of original lactose degradation (measured by HPLC). De-proteination of MCP by acidification prior to isomerisation helped lactulose formation in the earlier stages, but did not significantly increase the yield. The resulting lactulose MCP (40 °B) incorporated at the rate of 3–4% was effective in enhancing the growth rate and acid production of Lactobacillus acidophilus (LA-5) in probiotic products.