Effective valorization of bio-processed castor kernel meal based fish feed supplements concomitant with oil extraction processing industry: A prolific way towards greening of landscaping/environment

Abstract

The prime demand for expansion of feed-based aquaculture is the quest for new protein-rich ingredients to accomplish the global food and nutritional securities. Simultaneously, consistent production of agro-industrial wastes and their disposal is a major issue, although, the better nutritional profile of these wastes fostering a way forward to valorize in animal/fish feed. The present study was proposed to ensure the valorization of the castor oil industry’s residues i.e. castor cake or meal by standardizing the process for the preparation of protein isolate with the help of iso-electric precipitation method and subsequently utilizing them in fish feed. Maximum recoveries and protein content (P<0.05) for the castor protein isolate (CPI) were achieved at 12.0/5.0 pH combination. The nutritional quality of the protein isolate (CPI) was superior to the kernel meal and comparable to standard protein (egg white) and soybean protein isolates (SPI). In vivo evaluation of CPI was carried out in Labeo rohita fingerlings by feeding the different graded dietary level of CPI with substitution of 0%, 25%, 50%, 75%, and 100% soybean protein isolate based on equivalency of the protein. The diets were designated as control, CPI 25 , CPI 50 , CPI 75 , CPI 100 , respectively. The CPI contributed 0%, 11.83%, 22.78%, 33.28% and 43.91% of the total protein in experimental diets. Dietary castor protein isolate significantly affected the growth rate, feed conversion and nutrient utilization indices in L. rohita fingerlings. Maximum observed growth indices were in fish fed with control and CPI 25 , CPI 50 , and CPI 75 diets whereas, minimum in CPI 100 fed group. Dietary CPI did not affect the body indices, survival and body composition in rohu fingerlings. Based on the results, it can be concluded that castor protein isolate would be a valuable protein-rich ingredient for fish feed and 75% substitution of soy protein isolate with castor protein isolate could be possible without any harmful effects on growth, feed conversion, nutrient utilization and survival. • The method for preparation of castor protein isolate (CPI) was standardized. • The pH condition of 12.0/5.0 exhibited the best recoveries and protein content of CPI. • The nutritional value of CPI was superior to meal and comparable to egg white. • 75% substitution of soy protein isolate (SPI) with CPI is possible in carp diet. • CPI would be a potential protein source in animal/fish feed.