Abstract
Resource utilization of chrome shavings (CS) has attracted a lot of attention from scientists and technologists in leather industry. Especially, the collagen hydrolysates extracted from CS are expected to find potential application values in agricultural field. However, there is no biotoxicity analysis of collagen hydrolysates from CS. Herein, the collagen hydrolysates with different molecular weights were produced from CS by three hydrolysis dechroming methods including alkaline hydrolysis, enzymatic hydrolysis and alkaline-enzymatic synergistic hydrolysis, and the optimal hydrolysis process of CS was designed and conducted. To evaluate their toxicity, the three collagen hydrolysates were formulated into a nutrient solution for zebrafish development. The obtained results indicated that the hydrolysates with low concentrations (less than 0.6 mg/mL) were safe and could promote the development for zebrafish embryos. Furthermore, the three collagen hydrolysates were utilized as organic nitrogen sources and formulated into amino acid water-soluble fertilizers (AAWSF) including alkaline type fertilizer (OH), enzymatic type fertilizer (M) and alkaline-enzymatic type fertilizer (OH–M) for the early soilless seeding cultivation of wheat, soybean and rapeseed. It is worth mentioning that the chromium contents in the prepared AAWSF were less than 10 mg/kg, which is far less than the limit value in the standard (China, 50 mg/kg). The growth and development of seedlings (germination rate, plant height, fresh weight of leaves, soluble sugar content and chlorophyll content) were investigated. The corresponding results showed that the growth of seedlings watered with AAWSF was better compared with the other treatments, and the OH–M fertilizer had the best promoting effect on the seedlings growth and development, followed by the M and OH fertilizers. The safe toxicity assessment of the collagen hydrolysates will expand their application scope, and the use of collagen hydrolysates extracted from CS for seedlings growth also provides an effective and reasonable way to deal with the chromium-containing leather solid waste, which is an effective way to realize its resource utilization.Graphical
Highlights
Past decades have witnessed the rapid development of the leather industry
The hatchability, mortality, deformity, body length, pericardial area and 20 s heartbeats of zebrafish embryos were recorded at different exposure time
In all the collagen hydrolysates, the protein content was estimated by calculating the hydroxyproline (Hyp) content based on the standard curve of Hyp (Additional file 1: Fig. S1) because the Hyp is special and has relatively high content in collagen hydrolysate [36]
Summary
1 Introduction Past decades have witnessed the rapid development of the leather industry. Statistics showed that CS has been generated about 0.8 million tons in the world every year [4] Such a large number indicates that the problem of environmental pollution brought by CS is a thorny issue and challenge for the world, especially for the big countries in leather industry, such as India, China and Brazil. The hatchability, mortality, deformity, body length, pericardial area and 20 s heartbeats of zebrafish embryos were recorded at different exposure time These collagen hydrolysates were utilized to formulate different types of AAWSF for the germination and growth of three types of crops (wheat, soybean and rapeseed) in the early stage. The germination rate, plant height, fresh leaves weight, nitrogen (N), phosphorus (P), potassium (K), soluble sugar and chlorophyll contents were determined to estimate the efficiency of the fertilizers containing collagen hydrolysates with different MW
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