The Technology And Reaction Kinetics Of Biomass And Its Waste Hydrolysis For Amino Acids Production In Subcritical Water

In this paper, the biomass and its waste mainly refer to aquatic products (in lakes, rives and oceans), livestock, poultry and their waste, such as: fish and its guts, offal and scraps of discarded material which are produced in the course of processing; livestock, poultry and their waste like fur, feather, hogskin and pig offal, trim and other scraps residue produced in the course of processing; and the waste that are produced in restaurants and kitchens. Annual output of domestic animal (aquatic products, livestock and poultry) production has been enormous and has become an upward trend. Large numbers of biomass waste are produced from the processing of domestic animals every year, and the "yield" of international biomass waste each year is the more astonishing.Biomass as a substitute for fossil raw materials has attracted people's attention, as it is extensive and renewable resources. At present, although biomass products has a great yield, its added value is not high, and generally low utilization, even the huge surplus or expired biomass are disposed as waste. The biomass waste is often treated by landf'lll and stacking incineration way. So, it is an important and practical significance for human being to learn how to reasonably recycle biomass and its waste, improve the technology level, increase added value, lower production costs, reduce environmental pollution so that make a kind of renew resource and real realization of waste turned into treasure. The hydrolysis of biomass and its waste into high value-added products is a practical and effective recycle way. The currently industrial hydrolysis methods of biomass and its waste are chemical and enzymatic hydrolysis. But chemical hydrolysis reaction will bring serious environmental pollution, and with the shortcoming--amino acids easily be damaged; enzymatic hydrolysis is expensive, and with long production cycle. However, these methods and techniques not only make adequately use of biomass and its waste, but also bring secondary pollution to the environment. Therefore, the identification and development of a new hydrolysis method to overcome the shortcomings of chemical and enzymatic hydrolysis will be particularly important.Super(sub)-critical water technology is a recently developed new advanced technology, which has broad prospects for application in the field of environmental protection. Because organic pollutants or contaminations can be totally and quickly decomposed into harmless inorganic substances such as CO₂ and H₂O in super(sub)-critical water, no secondary pollution. Compared with the conventional solvent, the super(sub)- critical water have many advantages in ecology, economy and security. However it is becoming to be applied to the crucial organic reaction in industry as a kind of excellent solvent and appropriate reaction medium. So super(sub)-critical water chemical reaction caused widespread attention. Therefore, we investigated the hydrolysis of biological macromolecules (such as proteins, fats in biomass and its waste) into small biological molecules such as amino acids, organic acids and other chemical raw materials or intermediates in sub-critical water. Not only to solve the oversupply of raw material and environmental problems, but also make full use of resources, and produce greater economic benefits.This study contents include:1. biomass hydrolysis process optimization studyThe raw materials include fish, chicken, pork, fish offal, feathers and hair and so on. In the sub-critical water, the raw materials were hydrolyzed into amino acids, unsaturated fatty acids, polysaccharides and other high value-added products. The effects of temperature, pressure, reaction time and reaction atmosphere on biomass hydrolysis were investigated. By changing the reaction temperature, pressure, reaction time, technological parameters of maximum production yield of amino acid by biomass hydrolysis were achieved (shown in Table 3-1 to 3-9). Air, nitrogen and carbon dioxide were used as a reaction atmosphere, to identify the effect of atmosphere on amino acid yield. The results showed: nitrogen atmosphere suitable for the amino acid products of tyrosine, tryptophan and arginine; carbon dioxide atmosphere suitable for the amino acid products of histidine and iso-leucine; air atmosphere suitable for the amino acid products of leucine, serine, phenylalanine, alanine and lysine. The optimized process parameters of some amino acid products are shown in table 3-10, 3-11, 3-12.2. Biomass hydrolysates decolorization and recovery of lost amino acids in the decolorization processSub-critical hydrolysis process of biomass is often accompanied with the formation of a large number of pigment material, which seriously affected the separation of amino acids in hydrolysate by ion exchange way, therefore the hydrolysates have to be decolored to remove the pigment material. In this paper, activated carbon was used as a decoloring agent. The research targets including pH, activated carbon consumption, adsorption temperature and adsorption time, which were inspected to investigate the effects of decoloring pigment material in hydrolyzate. Decolorization optimum conditions of biomass hydrolysates: pH=4.0, the consumption amount of activated carbon=3g/100ml, time=15min, temperature=45℃. Under these conditions, decolorization rate is 90.28%, and amino acid loss rate is 51.38%.Recover lost amino acid: firstly, the activated carbon filter cake was desorbed by hydrochloric acid solution, then the amino acid crystal products was obtained by liquid condensation and crystallization. The recover conditions: pH=5.5, concentrated liquid volume: desorption liquid volume=1: 8, static retention time=12h. Under these conditions, the desorption rate is 91.72%.3. Crude separation techniques of mixed amino acid in biomass hydrolysates732 resin was selected as amino acid separation resins, ammonia as a washing agent, to explore the crude separation of mixed solution containing 18 kinds of amino acids. The effects of elution concentration, adsorption time and pH on the separation of mixed amino acids were investigated. The results showed: the amino acids in hydrolysates have separated into alkalescent amino acids, neutral amino acids and acidic amino acids. And the order of elution is neutral amino acids, alkalescent amino acids, acidic amino acids. The optimum condition: pH=2.0; velocity of hydrolysates into column=0.37ml^*min^-1; elution conditions is 300ml, 2.24mol^*L^-1 (ammonia eluting agent) at elution flow rate of 0.37ml^*min^-1.4. Biomass sub-critical hydrolysis kineticsThe hydrolysis kinetics study is conducted at temperature220℃, 240℃, 260℃. The hydrolysis yield of fish protein can be represented by amino acid yield from fish meat hydrolysis in sub-critical water. This result is used to define the ratio of hydrolyzed fish protein and obtain the formula of reaction kinetics. The reaction order is 1.6147. The velocity constant of total amino acids yield are 0.0017, 0.0045, 0.0097 at 220℃, 240℃, 260℃, respectively. The active energy is 96.774kJ/mol and the pre-exponential factor is 3.06456×10⁷.The main innovation1. Development of a new sub-critical protein hydrolysis process, which possesses simple, efficient, environmentally friendly features, is obtained.2. Studied biological protein hydrolysis kinetics by amino acids yield from biomass hydrolysis, and provided a new method for the kinetic study of biological protein hydrolysis.3. Explored the crude separation of complex mixed solution containing 18 kinds of amino acids.